From 0f11ad09f6287601f7d44d39baddd7068e872ad2 Mon Sep 17 00:00:00 2001
From: Adam Beckmeyer <adam_gpg@thebeckmeyers.xyz>
Date: Wed, 17 Apr 2019 22:42:00 -0400
Subject: [PATCH 1/3] Remove unnecessary splatting from internal interfaces

This gives a marginal improvement on speed and memory use during first
plot, but the biggest benefit is that it makes the code easier to read
and the profiling significantly easier to grok.
---
 src/Gadfly.jl       | 26 +++++++++++---------------
 src/aesthetics.jl   |  2 +-
 src/geom/subplot.jl |  8 ++++----
 src/guide.jl        |  2 +-
 src/scale.jl        | 27 +++++++++++++++------------
 5 files changed, 32 insertions(+), 33 deletions(-)

diff --git a/src/Gadfly.jl b/src/Gadfly.jl
index b517bc2af..6803719d8 100755
--- a/src/Gadfly.jl
+++ b/src/Gadfly.jl
@@ -653,7 +653,7 @@ function render_prepare(plot::Plot)
 
     # I. Scales
     layer_aess = Scale.apply_scales(IterTools.distinct(values(scales)),
-                                    datas..., subplot_datas...)
+                                    vcat(datas, subplot_datas))
 
     # set defaults for key titles
     keyvars = [:color, :shape]
@@ -692,7 +692,7 @@ function render_prepare(plot::Plot)
     end
 
     # IIb. Plot-wise Statistics
-    plot_aes = concat(layer_aess...)
+    plot_aes = concat(layer_aess)
     statistics = collect(statistics)
     Stat.apply_statistics(statistics, scales, coord, plot_aes)
 
@@ -809,28 +809,24 @@ function render_prepared(plot::Plot,
     # IV. Geometries
     themes = Theme[layer.theme === nothing ? plot.theme : layer.theme
                    for layer in plot.layers]
-    zips = trim_zip(plot.layers, layer_aess,
-                                                   layer_subplot_aess,
-                                                   layer_subplot_datas,
-               themes)
-
-    compose!(plot_context,
-             [compose(context(order=layer.order), render(layer.geom, theme, aes,
-                                                         subplot_aes, subplot_data,
-                                                         scales))
-              for (layer, aes, subplot_aes, subplot_data, theme) in zips]...)
+    zips = trim_zip(plot.layers, layer_aess, layer_subplot_aess,
+                    layer_subplot_datas, themes)
+    for (layer, aes, subplot_aes, subplot_data, theme) in zips
+        r = render(layer.geom, theme, aes, subplot_aes, subplot_data, scales)
+        compose!(plot_context, (context(order=layer.order), r))
+    end#for
 
     # V. Guides
-    guide_contexts = Any[]
+    guide_contexts = Guide.PositionedGuide[]
     for guide in guides
         guide_context = render(guide, plot.theme, plot_aes, dynamic)
-        if guide_context != nothing
+        if !isnothing(guide_context)
             append!(guide_contexts, guide_context)
         end
     end
 
     tbl = Guide.layout_guides(plot_context, coord,
-                              plot.theme, guide_contexts...)
+                              plot.theme, guide_contexts)
     if table_only
         return tbl
     end
diff --git a/src/aesthetics.jl b/src/aesthetics.jl
index 0ac515231..5dcb69b98 100755
--- a/src/aesthetics.jl
+++ b/src/aesthetics.jl
@@ -226,7 +226,7 @@ json(a::Aesthetics) = join([string(a, ":", json(getfield(a, var))) for var in ae
 # Returns:
 #   A new Aesthetics instance with vectors concatenated.
 #
-function concat(aess::Aesthetics...)
+function concat(aess)
     cataes = Aesthetics()
     for aes in aess
         for var in valid_aesthetics
diff --git a/src/geom/subplot.jl b/src/geom/subplot.jl
index 08bc4b113..bca1f4638 100644
--- a/src/geom/subplot.jl
+++ b/src/geom/subplot.jl
@@ -181,7 +181,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
                            Gadfly.Aesthetics[layer_aes_grid[k][i, j]
                                              for k in 1:length(geom.layers)],
                            Gadfly.Data[layer_data_grid[k][i, j]
-                                       for k in 1:length(geom.layers)]...)
+                                       for k in 1:length(geom.layers)])
 
         for (k, stats) in enumerate(layer_stats)
             Stat.apply_statistics(stats, scales, coord, layer_aes_grid[k][i, j])
@@ -190,7 +190,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
 
     # apply geom-wide statistics
     geom_aes = Gadfly.concat([layer_aes_grid[k][i,j]
-                              for i in 1:n, j in 1:m, k in 1:length(geom.layers)]...)
+                              for i in 1:n, j in 1:m, k in 1:length(geom.layers)])
     geom_stats = Gadfly.StatisticElement[]
 
     has_stat_xticks = false
@@ -220,7 +220,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
     if geom.free_x_axis
         for j in 1:m
             col_aes = Gadfly.concat([layer_aes_grid[k][i, j]
-                                     for i in 1:n, k in 1:length(geom.layers)]...)
+                                     for i in 1:n, k in 1:length(geom.layers)])
             Gadfly.inherit!(col_aes, geom_aes)
             Stat.apply_statistic(Stat.xticks(), scales, coord, col_aes)
 
@@ -231,7 +231,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
     if geom.free_y_axis
         for i in 1:n
             row_aes = Gadfly.concat([layer_aes_grid[k][i, j]
-                                     for j in 1:m, k in 1:length(geom.layers)]...)
+                                     for j in 1:m, k in 1:length(geom.layers)])
             Gadfly.inherit!(row_aes, geom_aes)
             Stat.apply_statistic(Stat.yticks(), scales, coord, row_aes)
 
diff --git a/src/guide.jl b/src/guide.jl
index 5e13b7c4c..400dca599 100644
--- a/src/guide.jl
+++ b/src/guide.jl
@@ -1129,7 +1129,7 @@ end
 function layout_guides(plot_context::Context,
                        coord::Gadfly.CoordinateElement,
                        theme::Gadfly.Theme,
-                       positioned_guides::PositionedGuide...)
+                       positioned_guides::Vector{PositionedGuide})
     # Organize guides by position
     guides = DefaultDict(() -> (Tuple{Vector{Context}, Int})[])
     for positioned_guide in positioned_guides
diff --git a/src/scale.jl b/src/scale.jl
index 6972591c4..be582ab93 100644
--- a/src/scale.jl
+++ b/src/scale.jl
@@ -19,9 +19,9 @@ include("color_misc.jl")
 iscategorical(scales::Dict{Symbol, Gadfly.ScaleElement}, var::Symbol) =
         haskey(scales, var) && isa(scales[var], DiscreteScale)
 
-function apply_scales(scales, aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+function apply_scales(scales, aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for scale in scales
-        apply_scale(scale, aess, datas...)
+        apply_scale(scale, aess, datas)
     end
 
     for (aes, data) in zip(aess, datas)
@@ -29,9 +29,9 @@ function apply_scales(scales, aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Dat
     end
 end
 
-function apply_scales(scales, datas::Gadfly.Data...)
+function apply_scales(scales, datas::Vector{Gadfly.Data})
     aess = Gadfly.Aesthetics[Gadfly.Aesthetics() for _ in datas]
-    apply_scales(scales, aess, datas...)
+    apply_scales(scales, aess, datas)
     aess
 end
 
@@ -178,9 +178,12 @@ alpha_continuous(; minvalue=0.0, maxvalue=1.0, labels=nothing, format=nothing, m
      ContinuousScale([:alpha], identity_transform, minvalue=minvalue, maxvalue=maxvalue,
                labels=labels, format=format, minticks=minticks, maxticks=maxticks, scalable=scalable)
 
+# Need to wrap Gadfly.Data in array for apply_scale methods
+apply_scale(scale::Gadfly.ScaleElement, aess::Vector{Gadfly.Aesthetics}, data::Gadfly.Data) =
+    apply_scale(scale, aess, Gadfly.Data[data])
 
 function apply_scale(scale::ContinuousScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
         for var in scale.vars
             vals = getfield(data, var)
@@ -363,7 +366,7 @@ alpha_discrete(; labels=nothing, levels=nothing, order=nothing) =
         DiscreteScale([:linestyle], labels=labels, levels=levels, order=order)
 
 
-function apply_scale(scale::DiscreteScale, aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+function apply_scale(scale::DiscreteScale, aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
         for var in scale.vars
             label_var = Symbol(var, "_label")
@@ -412,7 +415,7 @@ const color_none = NoneColorScale
 element_aesthetics(scale::NoneColorScale) = [:color]
 
 function apply_scale(scale::NoneColorScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for aes in aess
         aes.color = nothing
     end
@@ -430,7 +433,7 @@ const color_identity = IdentityColorScale
 element_aesthetics(scale::IdentityColorScale) = [:color]
 
 function apply_scale(scale::IdentityColorScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
         data.color === nothing && continue
         aes.color = discretize_make_ia(data.color)
@@ -513,7 +516,7 @@ end
 @deprecate discrete_color_manual(colors...; levels=nothing, order=nothing) color_discrete_manual(colors...; levels=levels, order=order)
 
 function apply_scale(scale::DiscreteColorScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     levelset = OrderedSet()
     for (aes, data) in zip(aess, datas)
         data.color === nothing && continue
@@ -621,7 +624,7 @@ const color_continuous_gradient = color_continuous  ### WHY HAVE THIS ALIAS?
 @deprecate continuous_color(;minvalue=nothing, maxvalue=nothing) color_continuous(;minvalue=nothing, maxvalue=nothing)
 
 function apply_scale(scale::ContinuousColorScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     cdata = skipmissing(Iterators.flatten(i.color for i in datas if i.color != nothing))
     if !isempty(cdata)
       cmin, cmax = extrema(cdata)
@@ -693,7 +696,7 @@ struct LabelScale <: Gadfly.ScaleElement
 end
 
 function apply_scale(scale::LabelScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
         data.label === nothing && continue
         aes.label = discretize(data.label)
@@ -733,7 +736,7 @@ end
 element_aesthetics(scale::IdentityScale) = [scale.var]
 
 function apply_scale(scale::IdentityScale,
-                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+                     aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
         getfield(data, scale.var) === nothing && continue
         setfield!(aes, scale.var, getfield(data, scale.var))

From bf5bd2ec7b6615bf15bbf5e96abad1f7e3db9965 Mon Sep 17 00:00:00 2001
From: Adam Beckmeyer <adam_gpg@thebeckmeyers.xyz>
Date: Thu, 18 Apr 2019 21:33:15 -0400
Subject: [PATCH 2/3] Compare nothing by type rather than by value

Comparing nothing by value (==, =!) rather than by identity (===, !==)
or by type (isnothing) can have negative consequences on code
speed. This commit changes all nothing comparisons to use the
isnothing utility added in Julia 1.1 and Compat 2.1.
---
 Project.toml         |   2 +-
 src/Gadfly.jl        |  35 +++++-----
 src/aesthetics.jl    |  55 +++++++--------
 src/coord.jl         |  48 +++++++-------
 src/data.jl          |   4 +-
 src/dataframes.jl    |   6 +-
 src/geom/bar.jl      |   4 +-
 src/geom/boxplot.jl  |   4 +-
 src/geom/errorbar.jl |   4 +-
 src/geom/hvabline.jl |  30 ++++-----
 src/geom/label.jl    |   4 +-
 src/geom/point.jl    |   2 +-
 src/geom/rectbin.jl  |   4 +-
 src/geom/segment.jl  |   2 +-
 src/geom/subplot.jl  |  14 ++--
 src/geometry.jl      |   2 +-
 src/guide.jl         |  66 +++++++++---------
 src/guide/keys.jl    |  10 +--
 src/mapping.jl       |   6 +-
 src/misc.jl          |   5 +-
 src/scale.jl         |  46 ++++++-------
 src/statistics.jl    | 155 ++++++++++++++++++++++---------------------
 src/ticks.jl         |   4 +-
 src/varset.jl        |   2 +-
 24 files changed, 255 insertions(+), 259 deletions(-)

diff --git a/Project.toml b/Project.toml
index ce84fa85c..b7663da4d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -34,7 +34,7 @@ StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 [compat]
 CategoricalArrays = "0.5"
 Colors = "0.9"
-Compat = "2"
+Compat = "2.1"
 Compose = "0.7"
 Contour = "0.5"
 CoupledFields = "0.1"
diff --git a/src/Gadfly.jl b/src/Gadfly.jl
index 6803719d8..c935e13e4 100755
--- a/src/Gadfly.jl
+++ b/src/Gadfly.jl
@@ -388,14 +388,14 @@ function render_prepare(plot::Plot)
     # they are missing.
     datas = Array{Data}(undef, length(plot.layers))
     for (i, layer) in enumerate(plot.layers)
-        if layer.data_source === nothing && isempty(layer.mapping)
+        if isnothing(layer.data_source) && isempty(layer.mapping)
             layer.data_source = plot.data_source
             layer.mapping = plot.mapping
             datas[i] = plot.data
         else
             datas[i] = Data()
 
-            if layer.data_source === nothing
+            if isnothing(layer.data_source)
                 layer.data_source = plot.data_source
             end
 
@@ -416,7 +416,7 @@ function render_prepare(plot::Plot)
         if isa(layer.geom, Geom.SubplotGeometry)
             for subplot_layer in layers(layer.geom)
                 subplot_data = Data()
-                if subplot_layer.data_source === nothing
+                if isnothing(subplot_layer.data_source)
                     subplot_layer.data_source = layer.data_source
                 end
 
@@ -434,7 +434,7 @@ function render_prepare(plot::Plot)
     coord = plot.coord
     for layer in plot.layers
         coord_type = element_coordinate_type(layer.geom)
-        if coord === nothing
+        if isnothing(coord)
             coord = coord_type()
         elseif typeof(coord) != coord_type
             error("Plot uses multiple coordinates: $(typeof(coord)) and $(coord_type)")
@@ -503,7 +503,7 @@ function render_prepare(plot::Plot)
 
     unscaled_aesthetics = setdiff(used_aesthetics, scaled_aesthetics)
 
-    _theme(plt, lyr) = lyr.theme == nothing ? plt.theme : lyr.theme
+    _theme(plt, lyr) = isnothing(lyr.theme) ? plt.theme : lyr.theme
 
     # Add default scales for statistics.
     layer_stats_with_theme = map(plot.layers, layer_stats) do l, stats
@@ -532,17 +532,17 @@ function render_prepare(plot::Plot)
         in(var, mapped_aesthetics) || continue
 
         var_data = getfield(plot.data, var)
-        if var_data == nothing
+        if isnothing(var_data)
             for data in datas
                 var_layer_data = getfield(data, var)
-                if var_layer_data != nothing
+                if !isnothing(var_layer_data)
                     var_data = var_layer_data
                     break
                 end
             end
         end
 
-        var_data == nothing && continue
+        isnothing(var_data) && continue
 
         t = classify_data(var_data)
         if scale_exists(t, var)
@@ -560,7 +560,7 @@ function render_prepare(plot::Plot)
         t = :categorical
         for data in Iterators.flatten((datas, subplot_datas))
             val = getfield(data, var)
-            if val != nothing && val != :categorical
+            if !isnothing(val) && val != :categorical
                 t = classify_data(val)
             end
         end
@@ -659,24 +659,27 @@ function render_prepare(plot::Plot)
     keyvars = [:color, :shape]
     for (i, layer) in enumerate(plot.layers)
         for kv in keyvars
-            fflag = (getfield(layer_aess[i], Symbol(kv,"_key_title")) == nothing) && haskey(layer.mapping, kv) && !isa(layer.mapping[kv], AbstractArray)
+            fflag = (isnothing(getfield(layer_aess[i], Symbol(kv,"_key_title")))) &&
+                haskey(layer.mapping, kv) &&
+                !isa(layer.mapping[kv], AbstractArray)
             fflag && setfield!(layer_aess[i], Symbol(kv,"_key_title"), string(layer.mapping[kv]))
         end
     end
 
     for kv in keyvars
-        fflag = (getfield(layer_aess[1], Symbol(kv,"_key_title")) == nothing) && haskey(plot.mapping, kv) && !isa(plot.mapping[kv], AbstractArray)
+        fflag = (isnothing(getfield(layer_aess[1], Symbol(kv,"_key_title")))) &&
+            haskey(plot.mapping, kv) && !isa(plot.mapping[kv], AbstractArray)
         fflag && setfield!(layer_aess[1], Symbol(kv,"_key_title"), string(plot.mapping[kv]))
     end
 
     # Auto-update color scale if shape==color
     catdatas = vcat(datas, subplot_datas)
     shapev = getfield.(catdatas, :shape)
-    di = (shapev.!=nothing) .& (shapev.== getfield.(catdatas, :color))
+    di = (!isnothing).(shapev) .& (shapev.== getfield.(catdatas, :color))
 
     supress_colorkey = false
     for (aes, data) in zip(layer_aess[di], catdatas[di])
-        aes.shape_key_title==nothing && (aes.shape_key_title=aes.color_key_title="Shape")
+        isnothing(aes.shape_key_title) && (aes.shape_key_title=aes.color_key_title="Shape")
         colorf = scales[:color].f
         scales[:color] =  Scale.color_discrete(colorf, levels=scales[:shape].levels, order=scales[:shape].order)
         Scale.apply_scale(scales[:color], [aes], Gadfly.Data(color=getfield(data,:color))  )
@@ -713,7 +716,7 @@ function render_prepare(plot::Plot)
 
     if !supress_keys
         for (KT, kv) in zip(keytypes, keyvars)
-            fflag = !all([getfield(aes, kv)==nothing for aes in [plot_aes, layer_aess...]])
+            fflag = !all([isnothing(getfield(aes, kv)) for aes in [plot_aes, layer_aess...]])
             fflag && !in(KT, explicit_guide_types) &&  push!(guides, KT())
         end
     end
@@ -756,7 +759,7 @@ function render(plot::Plot)
 
     ctx =  pad_inner(root_context, plot.theme.plot_padding...)
 
-    if plot.theme.background_color != nothing
+    if !isnothing(plot.theme.background_color)
         compose!(ctx, (context(order=-1000000),
                         fill(plot.theme.background_color),
                         stroke(nothing), rectangle()))
@@ -807,7 +810,7 @@ function render_prepared(plot::Plot,
                                           layer_aess), scales)
 
     # IV. Geometries
-    themes = Theme[layer.theme === nothing ? plot.theme : layer.theme
+    themes = Theme[isnothing(layer.theme) ? plot.theme : layer.theme
                    for layer in plot.layers]
     zips = trim_zip(plot.layers, layer_aess, layer_subplot_aess,
                     layer_subplot_datas, themes)
diff --git a/src/aesthetics.jl b/src/aesthetics.jl
index 5dcb69b98..ba5532f7b 100755
--- a/src/aesthetics.jl
+++ b/src/aesthetics.jl
@@ -102,7 +102,7 @@ function show(io::IO, data::Aesthetics)
     print(io, "Aesthetics(")
     for name in valid_aesthetics
         val = getfield(data, name)
-        if !ismissing(val) && val != nothing
+        if !ismissing(val) && !isnothing(val)
             print(io, "\n  ", string(name), "=")
             show(io, getfield(data, name))
         end
@@ -140,7 +140,7 @@ getindex(aes::Aesthetics, i::Integer, j::AbstractString) = getfield(aes, Symbol(
 function defined_aesthetics(aes::Aesthetics)
     vars = Set{Symbol}()
     for name in valid_aesthetics
-        getfield(aes, name) === nothing || push!(vars, name)
+        isnothing(getfield(aes, name)) || push!(vars, name)
     end
     vars
 end
@@ -172,7 +172,7 @@ function assert_aesthetics_undefined(who::AbstractString, aes::Aesthetics, vars:
 end
 
 function assert_aesthetics_equal_length(who::AbstractString, aes::Aesthetics, vars::Symbol...)
-    defined_vars = Compat.Iterators.filter(var -> !(getfield(aes, var) === nothing), vars)
+    defined_vars = Compat.Iterators.filter(var -> !isnothing(getfield(aes, var)), vars)
 
     if !isempty(defined_vars)
         n = length(getfield(aes, first(defined_vars)))
@@ -198,7 +198,7 @@ end
 #
 function update!(a::Aesthetics, b::Aesthetics)
     for name in valid_aesthetics
-        issomething(getfield(b, name)) && setfield(a, name, getfield(b, name))
+        !isnothing(getfield(b, name)) && setfield(a, name, getfield(b, name))
     end
     nothing
 end
@@ -230,22 +230,17 @@ function concat(aess)
     cataes = Aesthetics()
     for aes in aess
         for var in valid_aesthetics
-            if var in [:xviewmin, :yviewmin]
-                mu, mv = getfield(cataes, var), getfield(aes, var)
-                setfield!(cataes, var,
-                          mu === nothing ? mv :
-                             mv == nothing ? mu :
-                                 min(mu, mv))
-            elseif var in [:xviewmax, :yviewmax]
-                mu, mv = getfield(cataes, var), getfield(aes, var)
-                setfield!(cataes, var,
-                          mu === nothing ? mv :
-                             mv == nothing ? mu :
-                                 max(mu, mv))
+            mu, mv = getfield(cataes, var), getfield(aes, var)
+            isviewmin = var in (:xviewmin, :yviewmin)
+            isviewmax = var in (:xviewmax, :yviewmax)
+            mumv = if isviewmin
+                isnothing(mu) ? mv : isnothing(mv) ? mu : min(mu, mv)
+            elseif isviewmax
+                isnothing(mu) ? mv : isnothing(mv) ? mu : max(mu, mv)
             else
-                setfield!(cataes, var,
-                          cat_aes_var!(getfield(cataes, var), getfield(aes, var)))
-            end
+                cat_aes_var!(mu, mv)
+            end#if
+            setfield!(cataes, var, mumv)
         end
     end
     cataes
@@ -313,13 +308,13 @@ end
 #
 function by_xy_group(aes::T, xgroup, ygroup,
                      num_xgroups, num_ygroups) where T <: Union{Data, Aesthetics}
-    @assert xgroup === nothing || ygroup === nothing || length(xgroup) == length(ygroup)
+    @assert isnothing(xgroup) || isnothing(ygroup) || length(xgroup) == length(ygroup)
 
     n = num_ygroups
     m = num_xgroups
 
-    xrefs = xgroup === nothing ? [1] : xgroup
-    yrefs = ygroup === nothing ? [1] : ygroup
+    xrefs = isnothing(xgroup) ? [1] : xgroup
+    yrefs = isnothing(ygroup) ? [1] : ygroup
 
     aes_grid = Array{T}(undef, n, m)
     staging = Array{AbstractArray}(undef, n, m)
@@ -327,7 +322,7 @@ function by_xy_group(aes::T, xgroup, ygroup,
         aes_grid[i, j] = T()
     end
 
-    xgroup === nothing && ygroup === nothing && return aes_grid
+    isnothing(xgroup) && isnothing(ygroup) && return aes_grid
 
     function make_pooled_array(::Type{IndirectArray{T,N,A,V}}, arr::AbstractArray) where {T,N,A,V}
         uarr = unique(arr)
@@ -350,8 +345,8 @@ function by_xy_group(aes::T, xgroup, ygroup,
 
         vals = getfield(aes, var)
         if typeof(vals) <: AbstractArray
-            if xgroup !== nothing && length(vals) !== length(xgroup) ||
-               ygroup !== nothing && length(vals) !== length(ygroup)
+            if !isnothing(xgroup) && length(vals) !== length(xgroup) ||
+               !isnothing(ygroup) && length(vals) !== length(ygroup)
                 continue
             end
 
@@ -405,12 +400,12 @@ function inherit!(a::Aesthetics, b::Aesthetics;
         bval = getfield(b, field)
         if field in clobber_set
             setfield!(a, field, bval)
-        elseif aval === missing || aval === nothing || aval === string || aval == showoff
+        elseif aval === missing || isnothing(aval) || aval === string || aval === showoff
             setfield!(a, field, bval)
-        elseif field == :xviewmin || field == :yviewmin
-            bval != nothing && (aval == nothing || aval > bval) && setfield!(a, field, bval)
-        elseif field == :xviewmax || field == :yviewmax
-            bval != nothing && (aval == nothing || aval < bval) && setfield!(a, field, bval)
+        elseif field in (:xviewmin, :yviewmin) && !isnothing(bval)
+            (isnothing(aval) || aval > bval) && setfield!(a, field, bval)
+        elseif field in (:xviewmax, :yviewmax) && !isnothing(bval)
+            (isnothing(aval) || aval < bval) && setfield!(a, field, bval)
         elseif typeof(aval) <: Dict && typeof(bval) <: Dict
             merge!(aval, getfield(b, field))
         end
diff --git a/src/coord.jl b/src/coord.jl
index 5358591a1..d70837ff1 100644
--- a/src/coord.jl
+++ b/src/coord.jl
@@ -67,7 +67,7 @@ function first_concrete_aesthetic_value(aess::Vector{Gadfly.Aesthetics}, vars::V
     for var in vars
         for aes in aess
             vals = getfield(aes, var)
-            vals === nothing && continue
+            Gadfly.isnothing(vals) && continue
 
             if !isa(vals, AbstractArray)
                 vals = [vals]
@@ -106,7 +106,7 @@ function aesthetics_type(aess::Vector{Gadfly.Aesthetics},
     for var in vars
         for aes in aess
             vals = getfield(aes, var)
-            vals === nothing && continue
+            Gadfly.isnothing(vals) && continue
 
             if var == :outliers
                 if !isempty(vals)
@@ -153,11 +153,11 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
 
     xmin = xmax = first_concrete_aesthetic_value(aess, coord.xvars)
 
-    if xmin != nothing
+    if !Gadfly.isnothing(xmin)
         for var in coord.xvars
             for aes in aess
                 vals = getfield(aes, var)
-                vals === nothing && continue
+                Gadfly.isnothing(vals) && continue
 
                 if !isa(vals, AbstractArray)
                     vals = [vals]
@@ -169,11 +169,11 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
     end
 
     ymin = ymax = first_concrete_aesthetic_value(aess, coord.yvars)
-    if ymin != nothing
+    if !Gadfly.isnothing(ymin)
         for var in coord.yvars
             for aes in aess
                 vals = getfield(aes, var)
-                vals === nothing && continue
+                Gadfly.isnothing(vals) && continue
 
                 # Outliers is an odd aesthetic that needs special treatment.
                 if var == :outliers
@@ -196,40 +196,40 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
 
     # viewmin/max that is set explicitly should override min/max
     for aes in aess
-        if aes.xviewmin != nothing
-            xviewmin = xviewmin === nothing ? aes.xviewmin : min(xviewmin, aes.xviewmin)
+        if !Gadfly.isnothing(aes.xviewmin)
+            xviewmin = Gadfly.isnothing(xviewmin) ? aes.xviewmin : min(xviewmin, aes.xviewmin)
         end
 
-        if aes.xviewmax != nothing
-            xviewmax = xviewmax === nothing ? aes.xviewmax : max(xviewmax, aes.xviewmax)
+        if !Gadfly.isnothing(aes.xviewmax)
+            xviewmax = Gadfly.isnothing(xviewmax) ? aes.xviewmax : max(xviewmax, aes.xviewmax)
         end
 
-        if aes.yviewmin != nothing
-            yviewmin = yviewmin === nothing ? aes.yviewmin : min(yviewmin, aes.yviewmin)
+        if !Gadfly.isnothing(aes.yviewmin)
+            yviewmin = Gadfly.isnothing(yviewmin) ? aes.yviewmin : min(yviewmin, aes.yviewmin)
         end
 
-        if aes.yviewmax != nothing
-            yviewmax = yviewmax === nothing ? aes.yviewmax : max(yviewmax, aes.yviewmax)
+        if !Gadfly.isnothing(aes.yviewmax)
+            yviewmax = Gadfly.isnothing(yviewmax) ? aes.yviewmax : max(yviewmax, aes.yviewmax)
         end
     end
 
-    xmax = xviewmax === nothing ? xmax : max(xmax, xviewmax)
-    xmin = xviewmin === nothing ? xmin : min(xmin, xviewmin)
-    ymax = yviewmax === nothing ? ymax : max(ymax, yviewmax)
-    ymin = yviewmin === nothing ? ymin : min(ymin, yviewmin)
+    xmax = Gadfly.isnothing(xviewmax) ? xmax : max(xmax, xviewmax)
+    xmin = Gadfly.isnothing(xviewmin) ? xmin : min(xmin, xviewmin)
+    ymax = Gadfly.isnothing(yviewmax) ? ymax : max(ymax, yviewmax)
+    ymin = Gadfly.isnothing(yviewmin) ? ymin : min(ymin, yviewmin)
 
     # Hard limits set in Coord should override everything else
-    xmin = coord.xmin === nothing ? xmin : coord.xmin
-    xmax = coord.xmax === nothing ? xmax : coord.xmax
-    ymin = coord.ymin === nothing ? ymin : coord.ymin
-    ymax = coord.ymax === nothing ? ymax : coord.ymax
+    xmin = Gadfly.isnothing(coord.xmin) ? xmin : coord.xmin
+    xmax = Gadfly.isnothing(coord.xmax) ? xmax : coord.xmax
+    ymin = Gadfly.isnothing(coord.ymin) ? ymin : coord.ymin
+    ymax = Gadfly.isnothing(coord.ymax) ? ymax : coord.ymax
 
-    if xmin === nothing || !isfinite(xmin)
+    if Gadfly.isnothing(xmin) || !isfinite(xmin)
         xmin = 0.0
         xmax = 1.0
     end
 
-    if ymin === nothing || !isfinite(ymin)
+    if Gadfly.isnothing(ymin) || !isfinite(ymin)
         ymin = 0.0
         ymax = 1.0
     end
diff --git a/src/data.jl b/src/data.jl
index d8334b016..21fa375c7 100644
--- a/src/data.jl
+++ b/src/data.jl
@@ -62,7 +62,7 @@ function chain(ds::Data...)
     chained_data = Data()
     for name in data_fields
         vs = Any[getfield(d, name) for d in ds]
-        vs = Any[v for v in filter(issomething, vs)]
+        vs = Any[v for v in filter(!isnothing, vs)]
         if isempty(vs)
             setfield!(chained_data, name, nothing)
         else
@@ -78,7 +78,7 @@ function show(io::IO, data::Data)
     maxlen = 0
     print(io, "Data(")
     for name in data_fields
-        if getfield(data, name) != nothing
+        if !isnothing(getfield(data, name))
             print(io, "\n  ", string(name), "=")
             show(io, getfield(data, name))
         end
diff --git a/src/dataframes.jl b/src/dataframes.jl
index 622237fd4..2a7c6ddf3 100644
--- a/src/dataframes.jl
+++ b/src/dataframes.jl
@@ -11,7 +11,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
     vm = um
     grouped_columns = Set{Symbol}()
     for colgroup in colgroups
-        if colgroup.columns===nothing # null => group all columns
+        if isnothing(colgroup.columns) # null => group all columns
             vm *= un
             grouped_columns = copy(allcolumns)
         else
@@ -34,7 +34,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
 
     # allocate vectors for grouped columns
     for (j, colgroup) in enumerate(colgroups)
-        cols = colgroup.columns===nothing ? allcolumns : colgroup.columns
+        cols = isnothing(colgroup.columns) ? allcolumns : colgroup.columns
 
         # figure the grouped common column type
         firstcol = U[first(cols)]
@@ -64,7 +64,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
     col_indicators = Array{Symbol}(undef, vm, length(colgroups))
     row_indicators = Array{Int}(undef, vm, length(colgroups))
 
-    colidxs = [colgroup.columns===nothing ? collect(allcolumns) : colgroup.columns
+    colidxs = [isnothing(colgroup.columns) ? collect(allcolumns) : colgroup.columns
                for colgroup in colgroups]
 
     vi = 1
diff --git a/src/geom/bar.jl b/src/geom/bar.jl
index 697de3061..6348072c2 100644
--- a/src/geom/bar.jl
+++ b/src/geom/bar.jl
@@ -74,7 +74,7 @@ function render_bar(geom::BarGeometry,
             svgclass("geometry"))
     end
 
-    cs = aes.color === nothing ? theme.default_color : aes.color
+    cs = isnothing(aes.color) ? theme.default_color : aes.color
     compose!(ctx, fill(cs), svgclass("geometry"))
     if isa(theme.bar_highlight, Function)
         compose!(ctx, stroke(theme.bar_highlight(theme.default_color)))
@@ -272,7 +272,7 @@ function render(geom::BarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
         error("Orientation must be :horizontal or :vertical")
     end
 
-    if aes.color === nothing
+    if isnothing(aes.color)
         ctx = render_bar(geom, theme, aes, geom.orientation)
     elseif geom.position == :stack
         if geom.orientation == :horizontal
diff --git a/src/geom/boxplot.jl b/src/geom/boxplot.jl
index 0fc6222f2..f47cb55eb 100644
--- a/src/geom/boxplot.jl
+++ b/src/geom/boxplot.jl
@@ -123,7 +123,7 @@ function render(geom::BoxplotGeometry, theme::Gadfly.Theme, aes::Gadfly.Aestheti
         svgclass("geometry"))
 
     # Outliers
-    if !geom.suppress_outliers && aes.outliers != nothing && !isempty(aes.outliers)
+    if !geom.suppress_outliers && !isnothing(aes.outliers) && !isempty(aes.outliers)
         xys = collect(Iterators.flatten(zip(cycle([x]), ys, cycle([c]))
                              for (x, ys, c) in zip(xs, aes.outliers, cs)))
         compose!(ctx, (context(),
@@ -133,7 +133,7 @@ function render(geom::BoxplotGeometry, theme::Gadfly.Theme, aes::Gadfly.Aestheti
     end
 
     # Middle
-    if aes.middle != nothing
+    if !isnothing(aes.middle)
         compose!(ctx, (
            context(order=1),
            Compose.line([[(x - fw/2, mid), (x + fw/2, mid)]
diff --git a/src/geom/errorbar.jl b/src/geom/errorbar.jl
index 65dafa47b..67ce96d30 100644
--- a/src/geom/errorbar.jl
+++ b/src/geom/errorbar.jl
@@ -110,7 +110,7 @@ function render(geom::YErrorBarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthe
         stroke([theme.stroke_color(c) for c in aes.color]),
         linewidth(theme.line_width))
 
-    (aes.color_key_continuous == true || aes.color == nothing) || compose!(ctx,
+    (aes.color_key_continuous == true || isnothing(aes.color)) || compose!(ctx,
             svgclass([svg_color_class_from_label(aes.color_label([c])[1]) for c in aes.color]))
 
     return ctx
@@ -148,7 +148,7 @@ function render(geom::XErrorBarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthe
         stroke([theme.stroke_color(c) for c in aes.color]),
         linewidth(theme.line_width))
 
-    (aes.color_key_continuous == true || aes.color == nothing) || compose!(ctx,
+    (aes.color_key_continuous == true || isnothing(aes.color)) || compose!(ctx,
             svgclass([svg_color_class_from_label(aes.color_label([c])[1])
                       for c in aes.color]))
 
diff --git a/src/geom/hvabline.jl b/src/geom/hvabline.jl
index 70f5248a1..69fa4968f 100755
--- a/src/geom/hvabline.jl
+++ b/src/geom/hvabline.jl
@@ -18,7 +18,7 @@ struct HLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     HLineGeometry(color, size, style, tag) =
-            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 HLineGeometry(; color=nothing, size=nothing, style=nothing, tag=empty_tag) =
         HLineGeometry(color, size, style, tag)
@@ -36,9 +36,9 @@ element_aesthetics(::HLineGeometry) = [:yintercept]
 function render(geom::HLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("Geom.hline", aes, :yintercept)
 
-    color = geom.color === nothing ? theme.default_color : geom.color
-    size = geom.size === nothing ? theme.line_width : geom.size
-    style = geom.style === nothing ? theme.line_style[1] : geom.style
+    color = isnothing(geom.color) ? theme.default_color : geom.color
+    size = isnothing(geom.size) ? theme.line_width : geom.size
+    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.yintercept))
     size = check_arguments(size, length(aes.yintercept))
@@ -65,7 +65,7 @@ struct VLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     VLineGeometry(color, size, style, tag) =
-            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 VLineGeometry(; color=nothing, size=nothing, style=nothing, tag=empty_tag) =
         VLineGeometry(color, size, style, tag)
@@ -83,9 +83,9 @@ element_aesthetics(::VLineGeometry) = [:xintercept]
 function render(geom::VLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("Geom.vline", aes, :xintercept)
 
-    color = geom.color === nothing ? theme.default_color : geom.color
-    size = geom.size === nothing ? theme.line_width : geom.size
-    style = geom.style === nothing ? theme.line_style[1] : geom.style
+    color = isnothing(geom.color) ? theme.default_color : geom.color
+    size = isnothing(geom.size) ? theme.line_width : geom.size
+    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.xintercept))
     size = check_arguments(size, length(aes.xintercept))
@@ -112,7 +112,7 @@ struct ABLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     ABLineGeometry(color, size, style, tag) =
-            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 ABLineGeometry(; color=nothing, size=nothing, style=nothing, tag::Symbol=empty_tag) =
         ABLineGeometry(color, size, style, tag)
@@ -131,19 +131,19 @@ const abline = ABLineGeometry
 element_aesthetics(geom::ABLineGeometry) = [:intercept, :slope]
 
 function render(geom::ABLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
-    if aes.intercept == nothing && aes.slope == nothing
+    if isnothing(aes.intercept) && isnothing(aes.slope)
         aes.intercept = [0]
         aes.slope = [1]
-    elseif aes.intercept == nothing
+    elseif isnothing(aes.intercept)
         aes.intercept = fill(0,length(aes.slope))
-    elseif aes.slope == nothing
+    elseif isnothing(aes.slope)
         aes.slope = fill(1,length(aes.intercept))
     end
     Gadfly.assert_aesthetics_equal_length("Geom.line", aes, element_aesthetics(geom)...)
 
-    color = geom.color === nothing ? theme.default_color : geom.color
-    size = geom.size === nothing ? theme.line_width : geom.size
-    style = geom.style === nothing ? theme.line_style[1] : geom.style
+    color = isnothing(geom.color) ? theme.default_color : geom.color
+    size = isnothing(geom.size) ? theme.line_width : geom.size
+    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.intercept))
     size = check_arguments(size, length(aes.intercept))
diff --git a/src/geom/label.jl b/src/geom/label.jl
index a26ee82e7..48fca4d70 100644
--- a/src/geom/label.jl
+++ b/src/geom/label.jl
@@ -50,7 +50,7 @@ function deferred_label_context(geom::LabelGeometry,
 
     num_labels = length(aes.label)
 
-    if aes.size == nothing
+    if isnothing(aes.size)
         padding = fill(theme.point_size, num_labels) .+ theme.label_padding
     else
         padding = aes.size .+ theme.label_padding
@@ -279,7 +279,7 @@ function render(geom::LabelGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics
         end
 
         hpos, vpos, xoff, yoff = label_layouts[geom.position]
-        if aes.size == nothing
+        if isnothing(aes.size)
             offsets = [(xoff*(theme.point_size + theme.label_padding),
                         yoff*(theme.point_size + theme.label_padding))]
         else
diff --git a/src/geom/point.jl b/src/geom/point.jl
index dd35ab2a0..beabffa94 100644
--- a/src/geom/point.jl
+++ b/src/geom/point.jl
@@ -67,7 +67,7 @@ function render(geom::PointGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics
     for (x, y, color, size, shape, alpha) in Compose.cyclezip(aes.x, aes.y, aes.color, aes.size, aes.shape, aes_alpha)
         shapefun = typeof(shape) <: Function ? shape : theme.point_shapes[shape]
         sizeval = typeof(size) <: Int ? interpolate_size(size) : size
-        strokecolor = aes.color_key_continuous != nothing && aes.color_key_continuous ?
+        strokecolor = !isnothing(aes.color_key_continuous) && aes.color_key_continuous ?
                     theme.continuous_highlight_color(color) :
                     theme.discrete_highlight_color(color)
         class = svg_color_class_from_label(aes.color_label([color])[1])
diff --git a/src/geom/rectbin.jl b/src/geom/rectbin.jl
index 9b64363ff..b998fac0f 100644
--- a/src/geom/rectbin.jl
+++ b/src/geom/rectbin.jl
@@ -94,14 +94,14 @@ function render(geom::RectangularBinGeometry, theme::Gadfly.Theme, aes::Gadfly.A
 
     allvisible = true
     for c in cs
-        if c == nothing
+        if isnothing(c)
             allvisible = false
             break
         end
     end
 
     if !allvisible
-        visibility = cs .!= nothing
+        visibility = (!isnothing).(cs)
         cs = cs[visibility]
         xmin = xmin[visibility]
         xmax = xmax[visibility]
diff --git a/src/geom/segment.jl b/src/geom/segment.jl
index 499763686..a7fc70ae7 100755
--- a/src/geom/segment.jl
+++ b/src/geom/segment.jl
@@ -82,7 +82,7 @@ function render(geom::SegmentGeometry, theme::Gadfly.Theme, aes::Gadfly.Aestheti
 
     if geom.arrow
         check = [aes.xviewmin, aes.xviewmax, aes.yviewmin, aes.yviewmax ]
-        if any( map(x -> x === nothing, check) )
+        if any(map(isnothing, check))
             error("For Geom.vector, Scale minvalue and maxvalue must be manually provided for both axes")
         end
          xyrange = [aes.xviewmax-aes.xviewmin, aes.yviewmax-aes.yviewmin]
diff --git a/src/geom/subplot.jl b/src/geom/subplot.jl
index bca1f4638..a4c247780 100644
--- a/src/geom/subplot.jl
+++ b/src/geom/subplot.jl
@@ -136,7 +136,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         inherited_aes = element_aesthetics(layer.geom)
         push!(inherited_aes, :xgroup, :ygroup)
         for var in inherited_aes
-            if getfield(layer_aes, var) === nothing
+            if isnothing(getfield(layer_aes, var))
                 setfield!(layer_aes, var, getfield(superplot_aes, var))
             end
         end
@@ -144,17 +144,17 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
  # z
     for (layer_data, layer_aes) in zip(subplot_layer_datas, subplot_layer_aess)
         z = getfield(layer_data, :z)
-        (z != nothing) && setfield!(layer_aes, :z, z)
+        (!isnothing(z)) && setfield!(layer_aes, :z, z)
     end
 
     # work out the grid size
     m = 1
     n = 1
     for layer_aes in subplot_layer_aess
-        if layer_aes.xgroup != nothing
+        if !isnothing(layer_aes.xgroup)
             m = max(m, maximum(layer_aes.xgroup))
         end
-        if layer_aes.ygroup != nothing
+        if !isnothing(layer_aes.ygroup)
             n = max(n, maximum(layer_aes.ygroup))
         end
     end
@@ -315,7 +315,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         if i == n
             push!(guides, get(geom.guides, Guide.XTicks, Guide.xticks()))
 
-            if superplot_aes.xgroup !== nothing
+            if !isnothing(superplot_aes.xgroup)
                 push!(guides, get(geom.guides, Guide.XLabel, Guide.xlabel(xlabels[j])))
             end
         else
@@ -326,7 +326,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         if j == 1
             joff += 1
             push!(guides, get(geom.guides, Guide.YTicks, Guide.yticks()))
-            if superplot_aes.ygroup !== nothing
+            if !isnothing(superplot_aes.ygroup)
                 joff += 1
                 push!(guides, get(geom.guides, Guide.YLabel, Guide.ylabel(ylabels[i])))
             end
@@ -349,7 +349,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         # copy over the correct units, since we are reparenting the children
         for u in 1:size(subtbl, 1), v in 1:size(subtbl, 2)
             for child in subtbl[u, v]
-                if child.units===nothing
+                if isnothing(child.units)
                     child.units = subtbl.units
                 end
             end
diff --git a/src/geometry.jl b/src/geometry.jl
index 125410f34..377bf07b3 100644
--- a/src/geometry.jl
+++ b/src/geometry.jl
@@ -13,7 +13,7 @@ import Compose.combine # Prevent DataFrame.combine from taking over.
 import Gadfly: render, layers, element_aesthetics, inherit, escape_id,
                default_statistic, default_scales, element_coordinate_type,
                ScaleElement, svg_color_class_from_label, isconcrete,
-               concretize, discretize_make_ia
+               concretize, discretize_make_ia, isnothing
 import IterTools: distinct, takestrict
 import Compat.Iterators: cycle, product, repeated
 
diff --git a/src/guide.jl b/src/guide.jl
index 400dca599..32162cbca 100644
--- a/src/guide.jl
+++ b/src/guide.jl
@@ -9,7 +9,7 @@ using IterTools
 using JSON
 
 import Gadfly: render, escape_id, default_statistic, jsdata, jsplotdata,
-               svg_color_class_from_label
+               svg_color_class_from_label, isnothing
 
 
 # Where the guide should be placed in relation to the plot.
@@ -35,7 +35,7 @@ const questionmark = QuestionMark
 
 function render(guide::QuestionMark, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    text_color = theme.background_color == nothing ?
+    text_color = isnothing(theme.background_color) ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_box = compose!( context(),
         text(1w,0h+2px,"?",hright,vtop),
@@ -64,7 +64,7 @@ const helpscreen = HelpScreen
 
 function render(guide::HelpScreen, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    box_color = theme.background_color == nothing ?
+    box_color = isnothing(theme.background_color) ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_color = distinguishable_colors(2,box_color)[2]
     text_strings = ["h,j,k,l,arrows,drag to pan",
@@ -104,7 +104,7 @@ const crosshair = CrossHair
 
 function render(guide::CrossHair, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    text_color = theme.background_color == nothing ?
+    text_color = isnothing(theme.background_color) ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_box = compose!(
         context(),
@@ -262,7 +262,7 @@ function render_discrete_color_key(colors::Vector{C},
                     fill(theme.key_label_color))
 
                 col = compose!(context(xpos, yoff), swatches, swatch_labels)
-                if aes_color_label != nothing
+                if !isnothing(aes_color_label)
                     classes = [svg_color_class_from_label(aes_color_label([c])[1]) for c in cs]
                     #class_jscalls = ["data(\"color_class\", \"$(c)\")"
                                      #for c in classes]
@@ -395,7 +395,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
 
     (theme.key_position == :none || isempty(aes.color_key_colors)) && return PositionedGuide[]
     gpos = guide.pos
-    (theme.key_position == :inside && gpos === nothing) &&  (gpos = [0.7w, 0.25h])
+    (theme.key_position == :inside && isnothing(gpos)) &&  (gpos = [0.7w, 0.25h])
 
     used_colors = Set{Color}()
     colors = Array{Color}(undef, 0) # to preserve ordering
@@ -404,18 +404,18 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
     continuous_guide = false
     guide_title = guide.title
 
-    if guide_title === nothing && aes.color_key_title !== nothing
+    if isnothing(guide_title) && !isnothing(aes.color_key_title)
         guide_title = aes.color_key_title
     end
 
-    if aes.color_key_colors != nothing &&
-       aes.color_key_continuous != nothing &&
+    if !isnothing(aes.color_key_colors) &&
+       !isnothing(aes.color_key_continuous) &&
        aes.color_key_continuous
         continuous_guide = true
     end
 
     color_key_labels = aes.color_label(keys(aes.color_key_colors))
-    if !continuous_guide && (guide.labels != nothing)
+    if !continuous_guide && !isnothing(guide.labels)
         color_key_labels = guide.labels
     end
 
@@ -430,7 +430,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
         end
     end
 
-    if guide_title === nothing
+    if isnothing(guide_title)
         guide_title = "Color"
     end
 
@@ -457,7 +457,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
                                          title_width, theme)
     end
 
-    if aes.shape != nothing
+    if !isnothing(aes.shape)
         # TODO: Draw key for shapes. We need to think about how to make this
         # work. Do we need to optimize number of columns for shape and size
         # keys? I'm guessing it's not worth it.
@@ -469,7 +469,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
     end
 
     position = right_guide_position
-    if gpos != nothing
+    if !isnothing(gpos)
         position = over_guide_position
         ctxs = [compose(context(), (context(gpos[1],gpos[2]), ctxs[1]))]
     elseif theme.key_position == :left
@@ -517,11 +517,11 @@ function render(guide::ManualColorKey, theme::Gadfly.Theme,
 
     guide_title = guide.title
 
-    if guide_title === nothing && aes.color_key_title !== nothing
+    if isnothing(guide_title) && !isnothing(aes.color_key_title)
         guide_title = aes.color_key_title
     end
 
-    if guide_title === nothing
+    if isnothing(guide_title)
         guide_title = "Color"
     end
 
@@ -569,13 +569,13 @@ visibility.  `ticks` can also be an array of locations, or `nothing`.
 const xticks = XTicks
 
 default_statistic(guide::XTicks) =
-    guide.ticks == nothing ? Stat.identity() : Stat.xticks(ticks=guide.ticks)
+    isnothing(guide.ticks) ? Stat.identity() : Stat.xticks(ticks=guide.ticks)
 
 function render(guide::XTicks, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics, dynamic::Bool=true)
-    guide.ticks == nothing && return PositionedGuide[]
+    isnothing(guide.ticks) && return PositionedGuide[]
 
-    if Gadfly.issomething(aes.xtick)
+    if !Gadfly.isnothing(aes.xtick)
         ticks = aes.xtick
         tickvisibility = aes.xtickvisible
         scale = aes.xtickscale
@@ -592,7 +592,7 @@ function render(guide::XTicks, theme::Gadfly.Theme,
         scale = Any[]
     end
 
-    if Gadfly.issomething(aes.xgrid)
+    if !Gadfly.isnothing(aes.xgrid)
         grids = aes.xgrid
         gridvisibility = length(grids) < length(ticks) ?  tickvisibility[2:end] : tickvisibility
     else
@@ -740,7 +740,7 @@ visibility.  `ticks` can also be an array of locations, or `nothing`.
 const yticks = YTicks
 
 function default_statistic(guide::YTicks)
-    if guide.ticks == nothing
+    if isnothing(guide.ticks)
         return Stat.identity()
     else
         return Stat.yticks(ticks=guide.ticks)
@@ -749,11 +749,11 @@ end
 
 function render(guide::YTicks, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics, dynamic::Bool=true)
-    if guide.ticks == nothing
+    if isnothing(guide.ticks)
         return PositionedGuide[]
     end
 
-    if Gadfly.issomething(aes.ytick)
+    if !Gadfly.isnothing(aes.ytick)
         ticks = aes.ytick
         tickvisibility = aes.ytickvisible
         scale = aes.ytickscale
@@ -769,7 +769,7 @@ function render(guide::YTicks, theme::Gadfly.Theme,
         scale = Any[]
     end
 
-    if Gadfly.issomething(aes.ygrid)
+    if !Gadfly.isnothing(aes.ygrid)
         grids = aes.ygrid
         if length(grids) < length(ticks)
             gridvisibility = tickvisibility[2:end]
@@ -919,7 +919,7 @@ const xlabel = XLabel
 
 function render(guide::XLabel, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    if guide.label === nothing || isempty(guide.label)
+    if isnothing(guide.label) || isempty(guide.label)
         return nothing
     end
 
@@ -986,7 +986,7 @@ const ylabel = YLabel
 
 
 function render(guide::YLabel, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
-    if guide.label === nothing || isempty(guide.label)
+    if isnothing(guide.label) || isempty(guide.label)
         return nothing
     end
 
@@ -1044,7 +1044,7 @@ const title = Title
 
 function render(guide::Title, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    if guide.label === nothing || isempty(guide.label)
+    if isnothing(guide.label) || isempty(guide.label)
         return nothing
     end
 
@@ -1160,9 +1160,9 @@ function layout_guides(plot_context::Context,
     aspect_ratio = nothing
     if isa(coord, Gadfly.Coord.cartesian)
         if coord.fixed
-            aspect_ratio = plot_context.units===nothing ? 1.0 :
-                     abs(plot_context.units.width / plot_context.units.height)
-        elseif coord.aspect_ratio != nothing
+            aspect_ratio = isnothing(plot_context.units) ? 1.0 :
+                abs(plot_context.units.width / plot_context.units.height)
+        elseif !isnothing(coord.aspect_ratio)
             aspect_ratio = coord.aspect_ratio
         end
     end
@@ -1172,7 +1172,7 @@ function layout_guides(plot_context::Context,
     i = 1
     for (ctxs, order) in guides[top_guide_position]
         for ctx in ctxs
-            if ctx.units===nothing && plot_units!==nothing
+            if isnothing(ctx.units) && !isnothing(plot_units)
                 ctx.units = UnitBox(plot_units, toppad=0mm, bottompad=0mm)
             end
         end
@@ -1183,7 +1183,7 @@ function layout_guides(plot_context::Context,
     i += 1
     for (ctxs, order) in guides[bottom_guide_position]
         for ctx in ctxs
-            if ctx.units===nothing && plot_units!==nothing
+            if isnothing(ctx.units) && !isnothing(plot_units)
                 ctx.units = UnitBox(plot_units, toppad=0mm, bottompad=0mm)
             end
         end
@@ -1195,7 +1195,7 @@ function layout_guides(plot_context::Context,
     j = 1
     for (ctxs, order) in guides[left_guide_position]
         for ctx in ctxs
-            if ctx.units===nothing && plot_units!==nothing
+            if isnothing(ctx.units) && !isnothing(plot_units)
                 ctx.units = UnitBox(plot_units, leftpad=0mm, rightpad=0mm)
             end
         end
@@ -1206,7 +1206,7 @@ function layout_guides(plot_context::Context,
     j += 1
     for (ctxs, order) in guides[right_guide_position]
         for ctx in ctxs
-            if ctx.units===nothing && plot_units!==nothing
+            if isnothing(ctx.units) && !isnothing(plot_units)
                 ctx.units = UnitBox(plot_units, leftpad=0mm, rightpad=0mm)
             end
         end
diff --git a/src/guide/keys.jl b/src/guide/keys.jl
index ac3943033..d9d9d77b2 100644
--- a/src/guide/keys.jl
+++ b/src/guide/keys.jl
@@ -32,11 +32,11 @@ function Guide.render(guide::Guide.ShapeKey, theme::Gadfly.Theme, aes::Gadfly.Ae
 
     # Aesthetics for keys: shape_key_title, shape_label (Function), shape_key_shapes (AbstractDict)    
     nshapes = length(unique(aes.shape))
-    guide_title = (guide.title!="Shape" || aes.shape_key_title==nothing) ? guide.title : aes.shape_key_title
+    guide_title = (guide.title!="Shape" || isnothing(aes.shape_key_title)) ? guide.title : aes.shape_key_title
     shape_key_labels = !(guide.labels==[""]) ? guide.labels : aes.shape_label(1:nshapes)
     
     colors = [nothing]
-    if (aes.shape_key_title !=nothing)  && (aes.color_key_title==aes.shape_key_title)
+    if !isnothing(aes.shape_key_title)  && (aes.color_key_title==aes.shape_key_title)
         colors = collect(keys(aes.color_key_colors))
     end
     
@@ -70,8 +70,8 @@ function render_discrete_key(labels::Vector{String}, title_ctx::Context, title_w
 
     n = max(length(colors), length(shapes))
     shape1 = shapes[1]
-    shapes = (shape1==nothing) ? fill(theme.key_swatch_shape, n) : theme.point_shapes[shapes]
-    (colors[1]==nothing) && (colors = fill((theme.key_swatch_color==nothing) ? theme.default_color : theme.key_swatch_color, n))
+    shapes = isnothing(shape1) ? fill(theme.key_swatch_shape, n) : theme.point_shapes[shapes]
+    (isnothing(colors[1])) && (colors = fill((isnothing(theme.key_swatch_color)) ? theme.default_color : theme.key_swatch_color, n))
 
     # only consider layouts with a reasonable number of columns
     maxcols = theme.key_max_columns < 1 ? 1 : theme.key_max_columns
@@ -144,7 +144,7 @@ function render_discrete_key(labels::Vector{String}, title_ctx::Context, title_w
                     fill(theme.key_label_color))
 
                 col = compose!(context(xpos, yoff), swatches, swatch_labels)
-                if aes_color_label != nothing
+                if !isnothing(aes_color_label)
                     classes = [svg_color_class_from_label(aes_color_label([c])[1]) for c in clrs]
                     #class_jscalls = ["data(\"color_class\", \"$(c)\")" for c in classes]
                     compose!(col,
diff --git a/src/mapping.jl b/src/mapping.jl
index 12d625a58..9a7d9cc1b 100644
--- a/src/mapping.jl
+++ b/src/mapping.jl
@@ -87,7 +87,7 @@ end
 function meltdata(U::AbstractVector, colgroups_::Vector{Col.GroupedColumn})
     colgroups = Set(colgroups_)
 
-    if length(colgroups) != 1 || first(colgroups).columns!==nothing
+    if length(colgroups) != 1 || !isnothing(first(colgroups).columns)
         # if every column is of the same length, treat it as a matrix
         if length(Set([length(u for u in U)])) == 1
             return meltdata(cat(U..., dims=2), colgroups_)
@@ -130,7 +130,7 @@ function meltdata(U::AbstractMatrix, colgroups_::Vector{Col.GroupedColumn})
     vm = um
     grouped_columns = BitSet()
     for colgroup in colgroups
-        if colgroup.columns===nothing
+        if isnothing(colgroup.columns)
             vm *= un
             grouped_columns = copy(allcolumns)
         else
@@ -149,7 +149,7 @@ function meltdata(U::AbstractMatrix, colgroups_::Vector{Col.GroupedColumn})
     col_indicators = Array{Int}(undef, vm, length(colgroups))
     row_indicators = Array{Int}(undef, vm, length(colgroups))
 
-    colidxs = [colgroup.columns===nothing ? collect(allcolumns) : colgroup.columns
+    colidxs = [isnothing(colgroup.columns) ? collect(allcolumns) : colgroup.columns
                for colgroup in colgroups]
 
     vi = 1
diff --git a/src/misc.jl b/src/misc.jl
index 4a3591600..5ddbcd80a 100644
--- a/src/misc.jl
+++ b/src/misc.jl
@@ -178,7 +178,7 @@ function inherit!(a::T, b::T) where T
         aval = getfield(a, field)
         bval = getfield(b, field)
         # TODO: this is a hack to let non-default labelers overide the defaults
-        if aval === nothing || aval === string || aval == showoff
+        if isnothing(aval) || aval === string || aval == showoff
             setfield!(a, field, bval)
         elseif typeof(aval) <: Dict && typeof(bval) <: Dict
             merge!(aval, getfield(b, field))
@@ -188,9 +188,6 @@ function inherit!(a::T, b::T) where T
 end
 
 
-isnothing(u) = u === nothing
-issomething(u) = !isnothing(u)
-
 negate(f) = x -> !f(x)
 
 
diff --git a/src/scale.jl b/src/scale.jl
index be582ab93..a87692074 100644
--- a/src/scale.jl
+++ b/src/scale.jl
@@ -11,7 +11,7 @@ using CategoricalArrays
 using Printf
 
 import Gadfly: element_aesthetics, isconcrete, concrete_length, discretize_make_ia,
-    aes2str, valid_aesthetics
+    aes2str, valid_aesthetics, isnothing
 import Distributions: Distribution
 
 include("color_misc.jl")
@@ -86,7 +86,7 @@ struct ContinuousScale <: Gadfly.ScaleElement
     function ContinuousScale(vars, trans,
                              minvalue, maxvalue, minticks, maxticks,
                              labels, format, scalable)
-        minvalue != nothing && maxvalue != nothing && minvalue > maxvalue &&
+        !isnothing(minvalue) && !isnothing(maxvalue) && minvalue > maxvalue &&
                 error("Cannot construct a ContinuousScale with minvalue > maxvalue")
         new(vars, trans, minvalue, maxvalue, minticks, maxticks, labels, format, scalable)
     end
@@ -100,9 +100,9 @@ function ContinuousScale(vars, trans;
 end
 
 function make_labeler(scale::ContinuousScale)
-    if scale.labels != nothing
+    if !isnothing(scale.labels)
         xs -> [scale.labels(x) for x in xs]
-    elseif scale.format == nothing
+    elseif isnothing(scale.format)
         scale.trans.label
     else
         xs -> scale.trans.label(xs, scale.format)
@@ -190,7 +190,7 @@ function apply_scale(scale::ContinuousScale,
             if vals isa CategoricalArray
                 throw(ArgumentError("continuous scale for $var aesthetic when stored as a CategoricalArray. Consider using a discrete scale or convert data to an Array."))
             end
-            vals === nothing && continue
+            isnothing(vals) && continue
 
             # special case for function arrays bound to :y
             # pass the function values through and wait for the scale to
@@ -245,7 +245,7 @@ function apply_scale(scale::ContinuousScale,
             end
         end
 
-        if scale.minvalue != nothing
+        if !isnothing(scale.minvalue)
             if scale.vars === x_vars
                 aes.xviewmin = scale.trans.f(scale.minvalue)
             elseif scale.vars === y_vars
@@ -253,7 +253,7 @@ function apply_scale(scale::ContinuousScale,
             end
         end
 
-        if scale.maxvalue != nothing
+        if !isnothing(scale.maxvalue)
             if scale.vars === x_vars
                 aes.xviewmax = scale.trans.f(scale.maxvalue)
             elseif scale.vars === y_vars
@@ -272,7 +272,7 @@ end
 
 
 function discretize(values, levels=nothing, order=nothing, preserve_order=true)
-    if levels == nothing
+    if isnothing(levels)
         if preserve_order
             levels = OrderedSet()
             for value in values
@@ -286,7 +286,7 @@ function discretize(values, levels=nothing, order=nothing, preserve_order=true)
         da = discretize_make_ia(values, levels)
     end
 
-    if order != nothing
+    if !isnothing(order)
         return discretize_make_ia(da, da.values[order])
     else
         return da
@@ -370,13 +370,13 @@ function apply_scale(scale::DiscreteScale, aess::Vector{Gadfly.Aesthetics}, data
     for (aes, data) in zip(aess, datas)
         for var in scale.vars
             label_var = Symbol(var, "_label")
-            getfield(data, var) === nothing && continue
+            isnothing(getfield(data, var)) && continue
 
             disc_data = discretize(getfield(data, var), scale.levels, scale.order)
             setfield!(aes, var, discretize_make_ia(Int64.(disc_data.index)))
 
             # The leveler for discrete scales is a closure over the discretized data.
-            if scale.labels === nothing
+            if isnothing(scale.labels)
                 function default_labeler(xs)
                     lvls = filter(!ismissing, disc_data.values)
                     vals = Any[1 <= x <= length(lvls) ? lvls[x] : "" for x in xs]
@@ -435,7 +435,7 @@ element_aesthetics(scale::IdentityColorScale) = [:color]
 function apply_scale(scale::IdentityColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        data.color === nothing && continue
+        isnothing(data.color) && continue
         aes.color = discretize_make_ia(data.color)
         aes.color_key_colors = Dict()
     end
@@ -519,7 +519,7 @@ function apply_scale(scale::DiscreteColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     levelset = OrderedSet()
     for (aes, data) in zip(aess, datas)
-        data.color === nothing && continue
+        isnothing(data.color) && continue
         for d in data.color
             # Remove missing values
             # FixMe! The handling of missing values shouldn't be this scattered across the source
@@ -527,13 +527,13 @@ function apply_scale(scale::DiscreteColorScale,
         end
     end
 
-    if scale.levels == nothing
+    if isnothing(scale.levels)
         scale_levels = [levelset...]
         scale.preserve_order || sort!(scale_levels)
     else
         scale_levels = scale.levels
     end
-    scale.order == nothing || permute!(scale_levels, scale.order)
+    isnothing(scale.order) || permute!(scale_levels, scale.order)
     colors = convert(Vector{RGB{Float32}}, scale.f(length(scale_levels)))
 
     color_map = Dict([(color, string(label))
@@ -541,7 +541,7 @@ function apply_scale(scale::DiscreteColorScale,
     labeler(xs) = [color_map[x] for x in xs]
 
     for (aes, data) in zip(aess, datas)
-        data.color === nothing && continue
+        isnothing(data.color) && continue
         # Remove missing values
         # FixMe! The handling of missing values shouldn't be this scattered across the source
         ds = discretize([c for c in data.color if !ismissing(c)], scale_levels)
@@ -625,7 +625,7 @@ const color_continuous_gradient = color_continuous  ### WHY HAVE THIS ALIAS?
 
 function apply_scale(scale::ContinuousColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
-    cdata = skipmissing(Iterators.flatten(i.color for i in datas if i.color != nothing))
+    cdata = skipmissing(Iterators.flatten(i.color for i in datas if !isnothing(i.color)))
     if !isempty(cdata)
       cmin, cmax = extrema(cdata)
     else
@@ -633,9 +633,9 @@ function apply_scale(scale::ContinuousColorScale,
     end
 
     strict_span = false
-    scale.minvalue != nothing && scale.maxvalue != nothing && (strict_span=true)
-    scale.minvalue != nothing && (cmin=scale.minvalue)
-    scale.maxvalue != nothing && (cmax=scale.maxvalue)
+    !isnothing(scale.minvalue) && !isnothing(scale.maxvalue) && (strict_span=true)
+    !isnothing(scale.minvalue) && (cmin=scale.minvalue)
+    !isnothing(scale.maxvalue) && (cmax=scale.maxvalue)
 
     cmin, cmax = promote(cmin, cmax)
 
@@ -649,7 +649,7 @@ function apply_scale(scale::ContinuousColorScale,
     cspan = cmax != cmin ? cmax - cmin : 1.0
 
     for (aes, data) in zip(aess, datas)
-        data.color === nothing && continue
+        isnothing(data.color) && continue
 
         aes.color = Array{RGB{Float32}}(undef, length(data.color))
         apply_scale_typed!(aes.color, data.color, scale, cmin, cspan)
@@ -698,7 +698,7 @@ end
 function apply_scale(scale::LabelScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        data.label === nothing && continue
+        isnothing(data.label) && continue
         aes.label = discretize(data.label)
     end
 end
@@ -738,7 +738,7 @@ element_aesthetics(scale::IdentityScale) = [scale.var]
 function apply_scale(scale::IdentityScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        getfield(data, scale.var) === nothing && continue
+        isnothing(getfield(data, scale.var)) && continue
         setfield!(aes, scale.var, getfield(data, scale.var))
     end
 end
diff --git a/src/statistics.jl b/src/statistics.jl
index a55415ea5..6a2769d35 100644
--- a/src/statistics.jl
+++ b/src/statistics.jl
@@ -17,7 +17,8 @@ using LinearAlgebra
 using Random
 
 import Gadfly: Scale, Coord, input_aesthetics, output_aesthetics,
-               default_scales, isconcrete, setfield!, discretize_make_ia, aes2str
+    default_scales, isconcrete, setfield!, discretize_make_ia, aes2str,
+    isnothing
 import KernelDensity
 # import Distributions: Uniform, Distribution, qqbuild
 import IterTools: distinct
@@ -186,7 +187,7 @@ function apply_statistic(stat::BarStatistic,
 
     iscontinuous = haskey(scales, var) && isa(scales[var], Scale.ContinuousScale)
 
-    if getfield(aes, minvar) == nothing || getfield(aes, maxvar) == nothing
+    if isnothing(getfield(aes, minvar)) || isnothing(getfield(aes, maxvar))
         minvals, maxvals = barminmax(vals, iscontinuous)
 
         setfield!(aes, minvar, minvals)
@@ -194,13 +195,13 @@ function apply_statistic(stat::BarStatistic,
     end
 
     z = zero(eltype(getfield(aes, othervar)))
-    if getfield(aes, viewminvar) == nothing && z < minimum(getfield(aes, othervar))
+    if isnothing(getfield(aes, viewminvar)) && z < minimum(getfield(aes, othervar))
         setfield!(aes, viewminvar, z)
-    elseif getfield(aes, viewmaxvar) == nothing && z > maximum(getfield(aes, othervar))
+    elseif isnothing(getfield(aes, viewmaxvar)) && z > maximum(getfield(aes, othervar))
         setfield!(aes, viewmaxvar, z)
     end
 
-    if stat.position == :stack && aes.color !== nothing
+    if stat.position == :stack && !isnothing(aes.color)
         groups = Dict{Any,Float64}()
         for (x, y) in zip(getfield(aes, othervar), vals)
             Gadfly.isconcrete(x) || continue
@@ -214,11 +215,11 @@ function apply_statistic(stat::BarStatistic,
 
         viewmin, viewmax = extrema(values(groups))
         aes_viewminvar = getfield(aes, viewminvar)
-        if aes_viewminvar === nothing || aes_viewminvar > viewmin
+        if isnothing(aes_viewminvar) || aes_viewminvar > viewmin
             setfield!(aes, viewminvar, viewmin)
         end
         aes_viewmaxvar = getfield(aes, viewmaxvar)
-        if aes_viewmaxvar === nothing || aes_viewmaxvar < viewmax
+        if isnothing(aes_viewmaxvar) || aes_viewmaxvar < viewmax
             setfield!(aes, viewmaxvar, viewmax)
         end
     end
@@ -249,7 +250,7 @@ function HistogramStatistic(; bincount=nothing,
                               orientation=:vertical,
                               density=false,
                               limits=NamedTuple())
-    if bincount != nothing
+    if !isnothing(bincount)
         HistogramStatistic(bincount, bincount, position, orientation, density, limits)
     else
         HistogramStatistic(minbincount, maxbincount, position, orientation, density, limits)
@@ -340,7 +341,7 @@ function apply_statistic(stat::HistogramStatistic,
 
     stat.density && (bincounts = bincounts ./ (sum(bincounts) * binwidth))
 
-    if aes.color === nothing
+    if isnothing(aes.color)
         T = typeof(x_min + 1*binwidth)
         setfield!(aes, othervar, Array{Float64}(undef, d))
         setfield!(aes, minvar, Array{T}(undef, d))
@@ -398,7 +399,7 @@ function apply_statistic(stat::HistogramStatistic,
         if stat.position == :stack
             viewmax = Float64(maximum(stack_height))
             aes_viewmax = getfield(aes, viewmaxvar)
-            if aes_viewmax === nothing || aes_viewmax < viewmax
+            if isnothing(aes_viewmax) || aes_viewmax < viewmax
                 setfield!(aes, viewmaxvar, viewmax)
             end
         end
@@ -406,7 +407,7 @@ function apply_statistic(stat::HistogramStatistic,
         aes.color = discretize_make_ia(colors)
     end
 
-    getfield(aes, viewminvar) === nothing && setfield!(aes, viewminvar, 0.0)
+    isnothing(getfield(aes, viewminvar)) && setfield!(aes, viewminvar, 0.0)
 
     if haskey(scales, othervar)
         data = Gadfly.Data()
@@ -417,7 +418,7 @@ function apply_statistic(stat::HistogramStatistic,
         # See issue #560. Stacked histograms on a non-linear y scale are a strange
         # thing. After some discussion, the least confusing thing is to make the stack
         # partitioned linearly. Here we make that adjustment.
-        if stat.position == :stack && aes.color != nothing
+        if stat.position == :stack && !isnothing(aes.color)
             # A little trickery to figure out the scale stack height.
             data = Gadfly.Data()
             setfield!(data, othervar, stack_height)
@@ -511,7 +512,7 @@ function apply_statistic(stat::DensityStatistic,
                          aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("DensityStatistic", aes, :x)
 
-    if aes.color === nothing
+    if isnothing(aes.color)
         isa(aes.x[1], Real) || error("Kernel density estimation only works on Real types.")
 
         x_f64 = collect(Float64, aes.x)
@@ -561,12 +562,12 @@ function Histogram2DStatistic(; xbincount=nothing,
                                 ybincount=nothing,
                                 yminbincount=3,
                                 ymaxbincount=150)
-    if xbincount != nothing
+    if !isnothing(xbincount)
         xminbincount = xbincount
         xmaxbincount = xbincount
     end
 
-    if ybincount != nothing
+    if !isnothing(ybincount)
         yminbincount = ybincount
         ymaxbincount = ybincount
     end
@@ -770,7 +771,7 @@ function apply_statistic(stat::TickStatistic,
             error("TickStatistic cannot be applied to subplot coordinates.")
 
     # don't clobber existing ticks
-    getfield(aes, Symbol(stat.axis, "tick")) == nothing || return
+    isnothing(getfield(aes, Symbol(stat.axis, "tick"))) || return
 
     in_group_var = Symbol(stat.axis, "group")
     minval, maxval = nothing, nothing
@@ -781,11 +782,11 @@ function apply_statistic(stat::TickStatistic,
     for var in in_vars
         categorical && !in(var,[:x,:y]) && continue
         vals = getfield(aes, var)
-        if vals != nothing && eltype(vals) != Function
-            if minval == nothing
+        if !isnothing(vals) && eltype(vals) != Function
+            if isnothing(minval)
                 minval = first(vals)
             end
-            if maxval == nothing
+            if isnothing(maxval)
                 maxval = first(vals)
             end
             T = promote_type(typeof(minval), typeof(maxval))
@@ -794,14 +795,14 @@ function apply_statistic(stat::TickStatistic,
             maxval = convert(T, maxval)
 
             if stat.axis == "x"
-                dsize = aes.xsize === nothing ? [nothing] : aes.xsize
+                dsize = isnothing(aes.xsize) ? [nothing] : aes.xsize
             elseif stat.axis == "y"
-                dsize = aes.ysize === nothing ? [nothing] : aes.ysize
+                dsize = isnothing(aes.ysize) ? [nothing] : aes.ysize
             else
                 dsize = [nothing]
             end
 
-            size = aes.size === nothing ? [nothing] : aes.size
+            size = isnothing(aes.size) ? [nothing] : aes.size
 
             minval, maxval = apply_statistic_typed(minval, maxval, vals, size, dsize)
             push!(in_vals, vals)
@@ -824,17 +825,17 @@ function apply_statistic(stat::TickStatistic,
 
     # check the x/yviewmin/max pesudo-aesthetics
     if stat.axis == "x"
-        if aes.xviewmin != nothing
+        if !isnothing(aes.xviewmin)
             minval = min(minval, aes.xviewmin)
         end
-        if aes.xviewmax != nothing
+        if !isnothing(aes.xviewmax)
             maxval = max(maxval, aes.xviewmax)
         end
     elseif stat.axis == "y"
-        if aes.yviewmin != nothing
+        if !isnothing(aes.yviewmin)
             minval = min(minval, aes.yviewmin)
         end
-        if aes.yviewmax != nothing
+        if !isnothing(aes.yviewmax)
             maxval = max(maxval, aes.yviewmax)
         end
     end
@@ -843,20 +844,20 @@ function apply_statistic(stat::TickStatistic,
     strict_span = false
     if typeof(coord) == Coord.Cartesian
         if stat.axis == "x"
-            if coord.xmin !== nothing
+            if !isnothing(coord.xmin)
                 minval = coord.xmin
                 strict_span = true
             end
-            if coord.xmax !== nothing
+            if !isnothing(coord.xmax)
                 maxval = coord.xmax
                 strict_span = true
             end
         elseif stat.axis == "y"
-            if coord.ymin !== nothing
+            if !isnothing(coord.ymin)
                 minval = coord.ymin
                 strict_span = true
             end
-            if coord.ymax !== nothing
+            if !isnothing(coord.ymax)
                 maxval = coord.ymax
                 strict_span = true
             end
@@ -923,12 +924,12 @@ function apply_statistic(stat::TickStatistic,
     setfield!(aes, Symbol(stat.axis, "tickscale"), tickscale)
 
     viewmin_var = Symbol(stat.axis, "viewmin")
-    if getfield(aes, viewmin_var) === nothing || getfield(aes, viewmin_var) > viewmin
+    if isnothing(getfield(aes, viewmin_var)) || getfield(aes, viewmin_var) > viewmin
         setfield!(aes, viewmin_var, viewmin)
     end
 
     viewmax_var = Symbol(stat.axis, "viewmax")
-    if getfield(aes, viewmax_var) === nothing || getfield(aes, viewmax_var) < viewmax
+    if isnothing(getfield(aes, viewmax_var)) || getfield(aes, viewmax_var) < viewmax
         setfield!(aes, viewmax_var, viewmax)
     end
 
@@ -959,12 +960,12 @@ function minvalmaxval(minval::T, maxval::T, val, s, ds) where T
         maxval = val
     end
 
-    if s != nothing && typeof(s) <: AbstractFloat
+    if !isnothing(s) && typeof(s) <: AbstractFloat
         minval = min(minval, val - s)::T
         maxval = max(maxval, val + s)::T
     end
 
-    if ds != nothing
+    if !isnothing(ds)
         minval = min(minval, val - ds)::T
         maxval = max(maxval, val + ds)::T
     end
@@ -999,7 +1000,7 @@ function apply_statistic(stat::BoxplotStatistic,
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
 
-    xflag = aes.x != nothing
+    xflag = !isnothing(aes.x)
     aes_x = (xflag ? eltype(aes.x) : Int)[]
     if xflag
         aes_x = aes.x
@@ -1007,26 +1008,26 @@ function apply_statistic(stat::BoxplotStatistic,
         aes_x = ones(Int, length(aes.y))
         aes.x_label = x -> fill("", length(x))
     end
-    colorflag = aes.color != nothing
+    colorflag = !isnothing(aes.color)
     aes_color =  colorflag ? aes.color : fill(nothing, length(aes_x))
                      
-    if aes.y == nothing
+    if isnothing(aes.y)
         groups = Any[]
         for (x, c) in zip(aes.x, cycle(aes_color))
             push!(groups, (x, c))
         end
 
         yviewmin, yviewmax = minimum(aes.lower_fence), maximum(aes.upper_fence)
-        if aes.outliers !== nothing
+        if !isnothing(aes.outliers)
             yviewmin = minimum(yviewmin, aes.outliers)
             yviewmax = maximum(yviewmax, aes.outliers)
         end
 
-        if aes.yviewmin === nothing || aes.yviewmin > yviewmin
+        if isnothing(aes.yviewmin) || aes.yviewmin > yviewmin
             aes.yviewmin = yviewmin
         end
 
-        if aes.yviewmax === nothing || aes.yviewmax < yviewmax
+        if isnothing(aes.yviewmax) || aes.yviewmax < yviewmax
             aes.yviewmax = yviewmax
         end
     else
@@ -1082,11 +1083,11 @@ function apply_statistic(stat::BoxplotStatistic,
         xviewmin = xmin - minspan / 2
         xviewmax = xmax + minspan / 2
 
-        if aes.xviewmin === nothing || aes.xviewmin > xviewmin
+        if isnothing(aes.xviewmin) || aes.xviewmin > xviewmin
             aes.xviewmin = xviewmin
         end
 
-        if aes.xviewmax === nothing || aes.xviewmax < xviewmax
+        if isnothing(aes.xviewmax) || aes.xviewmax < xviewmax
             aes.xviewmax = xviewmax
         end
     end
@@ -1150,7 +1151,7 @@ function Stat.apply_statistic(stat::SmoothStatistic,
         error("Stat.loess and Stat.lm require that x and y be bound to arrays of plain numbers.")
     end
 
-    colorflag = aes.color != nothing
+    colorflag = !isnothing(aes.color)
     aes_color =  colorflag ? aes.color : fill(nothing, length(aes.x))
 
     uc = unique(aes_color)
@@ -1308,18 +1309,18 @@ function apply_statistic(stat::StepStatistic,
     p = sortperm(aes.x, alg=MergeSort)
     permute!(aes.x, p)
     permute!(aes.y, p)
-    aes.group != nothing && permute!(aes.group, p)
-    aes.color != nothing && permute!(aes.color, p)
+    !isnothing(aes.group) && permute!(aes.group, p)
+    !isnothing(aes.color) && permute!(aes.color, p)
 
-    if aes.group != nothing
+    if !isnothing(aes.group)
         Gadfly.assert_aesthetics_equal_length("StepStatistic", aes, :x, :group)
         permute!(aes.x, p)
         permute!(aes.y, p)
         permute!(aes.group, p)
-        aes.color != nothing && permute!(aes.color, p)
+        !isnothing(aes.color) && permute!(aes.color, p)
     end
 
-    if aes.color != nothing
+    if !isnothing(aes.color)
         Gadfly.assert_aesthetics_equal_length("StepStatistic", aes, :x, :color)
         # TODO: use this when we switch to 0.4
         # sortperm!(p, aes.color, alg=MergeSort, lt=Gadfly.color_isless)
@@ -1327,13 +1328,13 @@ function apply_statistic(stat::StepStatistic,
         permute!(aes.x, p)
         permute!(aes.y, p)
         permute!(aes.color, p)
-        aes.group != nothing && permute!(aes.group, p)
+        !isnothing(aes.group) && permute!(aes.group, p)
     end
 
     x_step = Array{eltype(aes.x)}(undef, 0)
     y_step = Array{eltype(aes.y)}(undef, 0)
-    color_step = aes.color == nothing ? nothing : Array{eltype(aes.color)}(undef, 0)
-    group_step = aes.group == nothing ? nothing : Array{eltype(aes.group)}(undef, 0)
+    color_step = isnothing(aes.color) ? nothing : Array{eltype(aes.color)}(undef, 0)
+    group_step = isnothing(aes.group) ? nothing : Array{eltype(aes.group)}(undef, 0)
 
     i = 1
     i_offset = 1
@@ -1343,17 +1344,17 @@ function apply_statistic(stat::StepStatistic,
 
         (u > length(aes.x) || v > length(aes.y)) && break
 
-        if (aes.color != nothing &&
+        if (!isnothing(aes.color) &&
              (aes.color[u] != aes.color[i_offset] || aes.color[v] != aes.color[i_offset])) ||
-           (aes.group != nothing &&
+           (!isnothing(aes.group) &&
              (aes.group[u] != aes.color[i_offset] || aes.color[v] != aes.group[i_offset]))
             i_offset = max(u, v)
             i = 1
         else
             push!(x_step, aes.x[u])
             push!(y_step, aes.y[v])
-            aes.color != nothing && push!(color_step, aes.color[i_offset])
-            aes.group != nothing && push!(group_step, aes.group[i_offset])
+            !isnothing(aes.color) && push!(color_step, aes.color[i_offset])
+            !isnothing(aes.group) && push!(group_step, aes.group[i_offset])
             i += 1
         end
     end
@@ -1405,7 +1406,7 @@ function apply_statistic(stat::FunctionStatistic,
     end
 
     # color was bound explicitly
-    if aes.color != nothing
+    if !isnothing(aes.color)
         func_color = aes.color
         aes.color = Array{eltype(aes.color)}(undef, length(aes.y) * stat.num_samples)
         groups = Array{Int}(undef, length(aes.y) * stat.num_samples)
@@ -1465,15 +1466,15 @@ function apply_statistic(stat::ContourStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    xs = aes.x === nothing ? nothing : convert(Vector{Float64}, aes.x)
-    ys = aes.y === nothing ? nothing : convert(Vector{Float64}, aes.y)
+    xs = isnothing(aes.x) ? nothing : convert(Vector{Float64}, aes.x)
+    ys = isnothing(aes.y) ? nothing : convert(Vector{Float64}, aes.y)
 
     if typeof(aes.z) <: Function
-        if xs == nothing && aes.xmin != nothing && aes.xmax != nothing
+        if isnothing(xs) && !isnothing(aes.xmin) && !isnothing(aes.xmax)
             xs = range(aes.xmin[1], stop=aes.xmax[1], length=stat.samples)
         end
 
-        if ys == nothing && aes.ymin != nothing && aes.ymax != nothing
+        if isnothing(ys) && !isnothing(aes.ymin) && !isnothing(aes.ymax)
             ys = range(aes.ymin[1], stop=aes.ymax[1], length=stat.samples)
         end
 
@@ -1482,10 +1483,10 @@ function apply_statistic(stat::ContourStatistic,
     elseif typeof(aes.z) <: Matrix
         zs = convert(Matrix{Float64}, aes.z)
 
-        if xs == nothing
+        if isnothing(xs)
             xs = collect(Float64, 1:size(zs)[1])
         end
-        if ys == nothing
+        if isnothing(ys)
             ys = collect(Float64, 1:size(zs)[2])
         end
         size(zs) != (length(xs), length(ys)) &&
@@ -1634,7 +1635,7 @@ function apply_statistic(stat::ViolinStatistic,
     grouped_color = Dict{Int, Gadfly.ColorOrNothing}(1=>nothing)
     ux = unique(aes.x)
     uxflag = length(ux) < length(aes.x)
-    colorflag = aes.color != nothing
+    colorflag = !isnothing(aes.color)
 
     uxflag && (grouped_y = Dict(x=>aes.y[aes.x.==x] for x in ux))
 
@@ -1701,7 +1702,7 @@ function minimum_span(vars::Vector{Symbol}, aes::Gadfly.Aesthetics)
             end
         end
 
-        if span == nothing || (dataspan != nothing && dataspan < span)
+        if isnothing(span) || (!isnothing(dataspan) && dataspan < span)
             span = dataspan
         end
     end
@@ -1714,7 +1715,7 @@ function apply_statistic(stat::JitterStatistic,
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
     span = minimum_span(stat.vars, aes)
-    span == nothing && return
+    isnothing(span) && return
 
     rng = MersenneTwister(stat.seed)
     for var in stat.vars
@@ -1755,7 +1756,7 @@ function apply_statistic(stat::BinMeanStatistic,
     Tx = eltype(aes.x)
     Ty = eltype(aes.y)
 
-    if aes.color === nothing
+    if isnothing(aes.color)
         (aes.x, aes.y) = mean_by_group(aes.x, aes.y, breaks)
     else
         groups = Dict()
@@ -1827,8 +1828,8 @@ function apply_statistic(stat::EnumerateStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    has_x = aes.x != nothing
-    has_y = aes.y != nothing
+    has_x = !isnothing(aes.x)
+    has_y = !isnothing(aes.y)
 
     if stat.var == :x && !has_x && has_y
         aes.x = collect(1:length(aes.y))
@@ -1869,14 +1870,14 @@ function apply_statistic(stat::VecFieldStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    xs = aes.x === nothing ? nothing : Float64.(aes.x)
-    ys = aes.y === nothing ? nothing : Float64.(aes.y)
+    xs = isnothing(aes.x) ? nothing : Float64.(aes.x)
+    ys = isnothing(aes.y) ? nothing : Float64.(aes.y)
 
     if isa(aes.z, Function)
-        if xs == nothing && aes.xmin != nothing && aes.xmax != nothing
+        if isnothing(xs) && !isnothing(aes.xmin) && !isnothing(aes.xmax)
             xs = range(aes.xmin[1], stop=aes.xmax[1], length=stat.samples)
         end
-        if ys == nothing && aes.ymin != nothing && aes.ymax != nothing
+        if isnothing(ys) && !isnothing(aes.ymin) && !isnothing(aes.ymax)
             ys = range(aes.ymin[1], stop=aes.ymax[1], length=stat.samples)
         end
 
@@ -1885,10 +1886,10 @@ function apply_statistic(stat::VecFieldStatistic,
     elseif isa(aes.z, Matrix)
         zs = Float64.(aes.z)
 
-        if xs == nothing
+        if isnothing(xs)
             xs = collect(Float64, 1:size(zs)[1])
         end
-        if ys == nothing
+        if isnothing(ys)
             ys = collect(Float64, 1:size(zs)[2])
         end
         if size(zs) != (length(xs), length(ys))
@@ -1981,8 +1982,8 @@ function apply_statistic(stat::EllipseStatistic,
     aes::Gadfly.Aesthetics)    
 
     Dat = [aes.x aes.y]
-    colorflag = aes.color != nothing
-    groupflag = aes.group != nothing
+    colorflag = !isnothing(aes.color)
+    groupflag = !isnothing(aes.group)
     aes_color = colorflag ? aes.color : fill(nothing, length(aes.x)) 
     aes_group = groupflag ? aes.group : fill(nothing, length(aes.x))
     CT, GT = eltype(aes_color), eltype(aes_group)
@@ -2053,7 +2054,7 @@ function apply_statistic(stat::DodgeStatistic,
                             coord::Gadfly.CoordinateElement,
                             aes::Gadfly.Aesthetics)
 
-    aes.color==nothing && return
+    isnothing(aes.color) && return
     nbars = length(unique(aes.color))
     othervar = (stat.axis == :x) ? :y : :x
     vals = getfield(aes, stat.axis)
diff --git a/src/ticks.jl b/src/ticks.jl
index aae6954d5..2e4c5710d 100644
--- a/src/ticks.jl
+++ b/src/ticks.jl
@@ -214,7 +214,7 @@ function optimize_ticks(x_min::DateTime, x_max::DateTime; extend_ticks::Bool=fal
                     # TODO: manually setting scale with :day, :minute, etc
                 end
 
-                if scale === nothing
+                if isnothing(scale)
                     for proposed_scale in [Day(1), Hour(1), Minute(1),
                                            Second(1), Millisecond(100),
                                            Millisecond(10), Millisecond(1)]
@@ -225,7 +225,7 @@ function optimize_ticks(x_min::DateTime, x_max::DateTime; extend_ticks::Bool=fal
                     end
                 end
 
-                if scale === nothing
+                if isnothing(scale)
                     scale = Millisecond(1)
                 end
 
diff --git a/src/varset.jl b/src/varset.jl
index 7773a18ce..9c3f31e42 100644
--- a/src/varset.jl
+++ b/src/varset.jl
@@ -45,7 +45,7 @@ macro varset(name::Symbol, table)
         push!(parameters, Expr(:kw, var, default))
         push!(inherit_parameters, Expr(:kw, var, :(b.$var)))
         if typ==:ColorOrNothing
-            push!(parsed_vars, :($(var)==nothing ? nothing : parse_colorant($(var))))
+            push!(parsed_vars, :(isnothing($(var)) ? nothing : parse_colorant($(var))))
         else
             push!(parsed_vars, :($(var)))
         end

From 80ae3df9c90ae8a241cb91f6f6e4b9322b0b1741 Mon Sep 17 00:00:00 2001
From: Adam Beckmeyer <adam_gpg@thebeckmeyers.xyz>
Date: Wed, 8 May 2019 15:43:00 -0400
Subject: [PATCH 3/3] Compare nothing values with ===

Per comment from @ararslan, the Julia compiler may prefer === versus
isnothing; improvements to be confirmed with benchmarking.
---
 src/Gadfly.jl        |  34 +++++-----
 src/aesthetics.jl    |  34 +++++-----
 src/coord.jl         |  48 +++++++-------
 src/data.jl          |   2 +-
 src/dataframes.jl    |   6 +-
 src/geom/bar.jl      |   4 +-
 src/geom/boxplot.jl  |   4 +-
 src/geom/errorbar.jl |   4 +-
 src/geom/hvabline.jl |  30 ++++-----
 src/geom/label.jl    |   4 +-
 src/geom/point.jl    |   2 +-
 src/geom/rectbin.jl  |   2 +-
 src/geom/subplot.jl  |  14 ++--
 src/geometry.jl      |   2 +-
 src/guide.jl         |  64 +++++++++---------
 src/guide/keys.jl    |  10 +--
 src/mapping.jl       |   6 +-
 src/misc.jl          |   2 +-
 src/scale.jl         |  46 ++++++-------
 src/statistics.jl    | 155 +++++++++++++++++++++----------------------
 src/ticks.jl         |   4 +-
 src/varset.jl        |   2 +-
 22 files changed, 239 insertions(+), 240 deletions(-)

diff --git a/src/Gadfly.jl b/src/Gadfly.jl
index c935e13e4..06edc7630 100755
--- a/src/Gadfly.jl
+++ b/src/Gadfly.jl
@@ -388,14 +388,14 @@ function render_prepare(plot::Plot)
     # they are missing.
     datas = Array{Data}(undef, length(plot.layers))
     for (i, layer) in enumerate(plot.layers)
-        if isnothing(layer.data_source) && isempty(layer.mapping)
+        if layer.data_source === nothing && isempty(layer.mapping)
             layer.data_source = plot.data_source
             layer.mapping = plot.mapping
             datas[i] = plot.data
         else
             datas[i] = Data()
 
-            if isnothing(layer.data_source)
+            if layer.data_source === nothing
                 layer.data_source = plot.data_source
             end
 
@@ -416,7 +416,7 @@ function render_prepare(plot::Plot)
         if isa(layer.geom, Geom.SubplotGeometry)
             for subplot_layer in layers(layer.geom)
                 subplot_data = Data()
-                if isnothing(subplot_layer.data_source)
+                if subplot_layer.data_source === nothing
                     subplot_layer.data_source = layer.data_source
                 end
 
@@ -434,7 +434,7 @@ function render_prepare(plot::Plot)
     coord = plot.coord
     for layer in plot.layers
         coord_type = element_coordinate_type(layer.geom)
-        if isnothing(coord)
+        if coord === nothing
             coord = coord_type()
         elseif typeof(coord) != coord_type
             error("Plot uses multiple coordinates: $(typeof(coord)) and $(coord_type)")
@@ -503,7 +503,7 @@ function render_prepare(plot::Plot)
 
     unscaled_aesthetics = setdiff(used_aesthetics, scaled_aesthetics)
 
-    _theme(plt, lyr) = isnothing(lyr.theme) ? plt.theme : lyr.theme
+    _theme(plt, lyr) = lyr.theme === nothing ? plt.theme : lyr.theme
 
     # Add default scales for statistics.
     layer_stats_with_theme = map(plot.layers, layer_stats) do l, stats
@@ -532,17 +532,17 @@ function render_prepare(plot::Plot)
         in(var, mapped_aesthetics) || continue
 
         var_data = getfield(plot.data, var)
-        if isnothing(var_data)
+        if var_data === nothing
             for data in datas
                 var_layer_data = getfield(data, var)
-                if !isnothing(var_layer_data)
+                if var_layer_data !== nothing
                     var_data = var_layer_data
                     break
                 end
             end
         end
 
-        isnothing(var_data) && continue
+        var_data === nothing && continue
 
         t = classify_data(var_data)
         if scale_exists(t, var)
@@ -560,7 +560,7 @@ function render_prepare(plot::Plot)
         t = :categorical
         for data in Iterators.flatten((datas, subplot_datas))
             val = getfield(data, var)
-            if !isnothing(val) && val != :categorical
+            if val !== nothing && val != :categorical
                 t = classify_data(val)
             end
         end
@@ -659,7 +659,7 @@ function render_prepare(plot::Plot)
     keyvars = [:color, :shape]
     for (i, layer) in enumerate(plot.layers)
         for kv in keyvars
-            fflag = (isnothing(getfield(layer_aess[i], Symbol(kv,"_key_title")))) &&
+            fflag = (getfield(layer_aess[i], Symbol(kv,"_key_title")) === nothing) &&
                 haskey(layer.mapping, kv) &&
                 !isa(layer.mapping[kv], AbstractArray)
             fflag && setfield!(layer_aess[i], Symbol(kv,"_key_title"), string(layer.mapping[kv]))
@@ -667,7 +667,7 @@ function render_prepare(plot::Plot)
     end
 
     for kv in keyvars
-        fflag = (isnothing(getfield(layer_aess[1], Symbol(kv,"_key_title")))) &&
+        fflag = (getfield(layer_aess[1], Symbol(kv,"_key_title")) === nothing) &&
             haskey(plot.mapping, kv) && !isa(plot.mapping[kv], AbstractArray)
         fflag && setfield!(layer_aess[1], Symbol(kv,"_key_title"), string(plot.mapping[kv]))
     end
@@ -675,11 +675,11 @@ function render_prepare(plot::Plot)
     # Auto-update color scale if shape==color
     catdatas = vcat(datas, subplot_datas)
     shapev = getfield.(catdatas, :shape)
-    di = (!isnothing).(shapev) .& (shapev.== getfield.(catdatas, :color))
+    di = @. (shapev !== nothing) & (shapev == getfield(catdatas, :color))
 
     supress_colorkey = false
     for (aes, data) in zip(layer_aess[di], catdatas[di])
-        isnothing(aes.shape_key_title) && (aes.shape_key_title=aes.color_key_title="Shape")
+        aes.shape_key_title === nothing && (aes.shape_key_title=aes.color_key_title="Shape")
         colorf = scales[:color].f
         scales[:color] =  Scale.color_discrete(colorf, levels=scales[:shape].levels, order=scales[:shape].order)
         Scale.apply_scale(scales[:color], [aes], Gadfly.Data(color=getfield(data,:color))  )
@@ -716,7 +716,7 @@ function render_prepare(plot::Plot)
 
     if !supress_keys
         for (KT, kv) in zip(keytypes, keyvars)
-            fflag = !all([isnothing(getfield(aes, kv)) for aes in [plot_aes, layer_aess...]])
+            fflag = !all([getfield(aes, kv) === nothing for aes in [plot_aes, layer_aess...]])
             fflag && !in(KT, explicit_guide_types) &&  push!(guides, KT())
         end
     end
@@ -759,7 +759,7 @@ function render(plot::Plot)
 
     ctx =  pad_inner(root_context, plot.theme.plot_padding...)
 
-    if !isnothing(plot.theme.background_color)
+    if plot.theme.background_color !== nothing
         compose!(ctx, (context(order=-1000000),
                         fill(plot.theme.background_color),
                         stroke(nothing), rectangle()))
@@ -810,7 +810,7 @@ function render_prepared(plot::Plot,
                                           layer_aess), scales)
 
     # IV. Geometries
-    themes = Theme[isnothing(layer.theme) ? plot.theme : layer.theme
+    themes = Theme[layer.theme === nothing ? plot.theme : layer.theme
                    for layer in plot.layers]
     zips = trim_zip(plot.layers, layer_aess, layer_subplot_aess,
                     layer_subplot_datas, themes)
@@ -823,7 +823,7 @@ function render_prepared(plot::Plot,
     guide_contexts = Guide.PositionedGuide[]
     for guide in guides
         guide_context = render(guide, plot.theme, plot_aes, dynamic)
-        if !isnothing(guide_context)
+        if guide_context !== nothing
             append!(guide_contexts, guide_context)
         end
     end
diff --git a/src/aesthetics.jl b/src/aesthetics.jl
index ba5532f7b..2617831a1 100755
--- a/src/aesthetics.jl
+++ b/src/aesthetics.jl
@@ -102,7 +102,7 @@ function show(io::IO, data::Aesthetics)
     print(io, "Aesthetics(")
     for name in valid_aesthetics
         val = getfield(data, name)
-        if !ismissing(val) && !isnothing(val)
+        if !ismissing(val) && val !== nothing
             print(io, "\n  ", string(name), "=")
             show(io, getfield(data, name))
         end
@@ -140,7 +140,7 @@ getindex(aes::Aesthetics, i::Integer, j::AbstractString) = getfield(aes, Symbol(
 function defined_aesthetics(aes::Aesthetics)
     vars = Set{Symbol}()
     for name in valid_aesthetics
-        isnothing(getfield(aes, name)) || push!(vars, name)
+        getfield(aes, name) === nothing || push!(vars, name)
     end
     vars
 end
@@ -172,7 +172,7 @@ function assert_aesthetics_undefined(who::AbstractString, aes::Aesthetics, vars:
 end
 
 function assert_aesthetics_equal_length(who::AbstractString, aes::Aesthetics, vars::Symbol...)
-    defined_vars = Compat.Iterators.filter(var -> !isnothing(getfield(aes, var)), vars)
+    defined_vars = Compat.Iterators.filter(var -> getfield(aes, var) !== nothing, vars)
 
     if !isempty(defined_vars)
         n = length(getfield(aes, first(defined_vars)))
@@ -198,7 +198,7 @@ end
 #
 function update!(a::Aesthetics, b::Aesthetics)
     for name in valid_aesthetics
-        !isnothing(getfield(b, name)) && setfield(a, name, getfield(b, name))
+        getfield(b, name) !== nothing && setfield(a, name, getfield(b, name))
     end
     nothing
 end
@@ -234,9 +234,9 @@ function concat(aess)
             isviewmin = var in (:xviewmin, :yviewmin)
             isviewmax = var in (:xviewmax, :yviewmax)
             mumv = if isviewmin
-                isnothing(mu) ? mv : isnothing(mv) ? mu : min(mu, mv)
+                mu === nothing ? mv : mv === nothing ? mu : min(mu, mv)
             elseif isviewmax
-                isnothing(mu) ? mv : isnothing(mv) ? mu : max(mu, mv)
+                mu === nothing ? mv : mv === nothing ? mu : max(mu, mv)
             else
                 cat_aes_var!(mu, mv)
             end#if
@@ -308,13 +308,13 @@ end
 #
 function by_xy_group(aes::T, xgroup, ygroup,
                      num_xgroups, num_ygroups) where T <: Union{Data, Aesthetics}
-    @assert isnothing(xgroup) || isnothing(ygroup) || length(xgroup) == length(ygroup)
+    @assert xgroup === nothing || ygroup === nothing || length(xgroup) == length(ygroup)
 
     n = num_ygroups
     m = num_xgroups
 
-    xrefs = isnothing(xgroup) ? [1] : xgroup
-    yrefs = isnothing(ygroup) ? [1] : ygroup
+    xrefs = xgroup === nothing ? [1] : xgroup
+    yrefs = ygroup === nothing ? [1] : ygroup
 
     aes_grid = Array{T}(undef, n, m)
     staging = Array{AbstractArray}(undef, n, m)
@@ -322,7 +322,7 @@ function by_xy_group(aes::T, xgroup, ygroup,
         aes_grid[i, j] = T()
     end
 
-    isnothing(xgroup) && isnothing(ygroup) && return aes_grid
+    xgroup === nothing && ygroup === nothing && return aes_grid
 
     function make_pooled_array(::Type{IndirectArray{T,N,A,V}}, arr::AbstractArray) where {T,N,A,V}
         uarr = unique(arr)
@@ -345,8 +345,8 @@ function by_xy_group(aes::T, xgroup, ygroup,
 
         vals = getfield(aes, var)
         if typeof(vals) <: AbstractArray
-            if !isnothing(xgroup) && length(vals) !== length(xgroup) ||
-               !isnothing(ygroup) && length(vals) !== length(ygroup)
+            if xgroup !== nothing && length(vals) !== length(xgroup) ||
+               ygroup !== nothing && length(vals) !== length(ygroup)
                 continue
             end
 
@@ -400,12 +400,12 @@ function inherit!(a::Aesthetics, b::Aesthetics;
         bval = getfield(b, field)
         if field in clobber_set
             setfield!(a, field, bval)
-        elseif aval === missing || isnothing(aval) || aval === string || aval === showoff
+        elseif aval === missing || aval === nothing || aval === string || aval === showoff
             setfield!(a, field, bval)
-        elseif field in (:xviewmin, :yviewmin) && !isnothing(bval)
-            (isnothing(aval) || aval > bval) && setfield!(a, field, bval)
-        elseif field in (:xviewmax, :yviewmax) && !isnothing(bval)
-            (isnothing(aval) || aval < bval) && setfield!(a, field, bval)
+        elseif field in (:xviewmin, :yviewmin) && bval !== nothing
+            (aval === nothing || aval > bval) && setfield!(a, field, bval)
+        elseif field in (:xviewmax, :yviewmax) && bval !== nothing
+            (aval === nothing || aval < bval) && setfield!(a, field, bval)
         elseif typeof(aval) <: Dict && typeof(bval) <: Dict
             merge!(aval, getfield(b, field))
         end
diff --git a/src/coord.jl b/src/coord.jl
index d70837ff1..9d3c1784a 100644
--- a/src/coord.jl
+++ b/src/coord.jl
@@ -67,7 +67,7 @@ function first_concrete_aesthetic_value(aess::Vector{Gadfly.Aesthetics}, vars::V
     for var in vars
         for aes in aess
             vals = getfield(aes, var)
-            Gadfly.isnothing(vals) && continue
+            vals === nothing && continue
 
             if !isa(vals, AbstractArray)
                 vals = [vals]
@@ -106,7 +106,7 @@ function aesthetics_type(aess::Vector{Gadfly.Aesthetics},
     for var in vars
         for aes in aess
             vals = getfield(aes, var)
-            Gadfly.isnothing(vals) && continue
+            vals === nothing && continue
 
             if var == :outliers
                 if !isempty(vals)
@@ -153,11 +153,11 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
 
     xmin = xmax = first_concrete_aesthetic_value(aess, coord.xvars)
 
-    if !Gadfly.isnothing(xmin)
+    if xmin !== nothing
         for var in coord.xvars
             for aes in aess
                 vals = getfield(aes, var)
-                Gadfly.isnothing(vals) && continue
+                vals === nothing && continue
 
                 if !isa(vals, AbstractArray)
                     vals = [vals]
@@ -169,11 +169,11 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
     end
 
     ymin = ymax = first_concrete_aesthetic_value(aess, coord.yvars)
-    if !Gadfly.isnothing(ymin)
+    if ymin !== nothing
         for var in coord.yvars
             for aes in aess
                 vals = getfield(aes, var)
-                Gadfly.isnothing(vals) && continue
+                vals === nothing && continue
 
                 # Outliers is an odd aesthetic that needs special treatment.
                 if var == :outliers
@@ -196,40 +196,40 @@ function apply_coordinate(coord::Cartesian, aess::Vector{Gadfly.Aesthetics},
 
     # viewmin/max that is set explicitly should override min/max
     for aes in aess
-        if !Gadfly.isnothing(aes.xviewmin)
-            xviewmin = Gadfly.isnothing(xviewmin) ? aes.xviewmin : min(xviewmin, aes.xviewmin)
+        if aes.xviewmin !== nothing
+            xviewmin = xviewmin === nothing ? aes.xviewmin : min(xviewmin, aes.xviewmin)
         end
 
-        if !Gadfly.isnothing(aes.xviewmax)
-            xviewmax = Gadfly.isnothing(xviewmax) ? aes.xviewmax : max(xviewmax, aes.xviewmax)
+        if aes.xviewmax !== nothing
+            xviewmax = xviewmax === nothing ? aes.xviewmax : max(xviewmax, aes.xviewmax)
         end
 
-        if !Gadfly.isnothing(aes.yviewmin)
-            yviewmin = Gadfly.isnothing(yviewmin) ? aes.yviewmin : min(yviewmin, aes.yviewmin)
+        if aes.yviewmin !== nothing
+            yviewmin = yviewmin === nothing ? aes.yviewmin : min(yviewmin, aes.yviewmin)
         end
 
-        if !Gadfly.isnothing(aes.yviewmax)
-            yviewmax = Gadfly.isnothing(yviewmax) ? aes.yviewmax : max(yviewmax, aes.yviewmax)
+        if aes.yviewmax !== nothing
+            yviewmax = yviewmax === nothing ? aes.yviewmax : max(yviewmax, aes.yviewmax)
         end
     end
 
-    xmax = Gadfly.isnothing(xviewmax) ? xmax : max(xmax, xviewmax)
-    xmin = Gadfly.isnothing(xviewmin) ? xmin : min(xmin, xviewmin)
-    ymax = Gadfly.isnothing(yviewmax) ? ymax : max(ymax, yviewmax)
-    ymin = Gadfly.isnothing(yviewmin) ? ymin : min(ymin, yviewmin)
+    xmax = xviewmax === nothing ? xmax : max(xmax, xviewmax)
+    xmin = xviewmin === nothing ? xmin : min(xmin, xviewmin)
+    ymax = yviewmax === nothing ? ymax : max(ymax, yviewmax)
+    ymin = yviewmin === nothing ? ymin : min(ymin, yviewmin)
 
     # Hard limits set in Coord should override everything else
-    xmin = Gadfly.isnothing(coord.xmin) ? xmin : coord.xmin
-    xmax = Gadfly.isnothing(coord.xmax) ? xmax : coord.xmax
-    ymin = Gadfly.isnothing(coord.ymin) ? ymin : coord.ymin
-    ymax = Gadfly.isnothing(coord.ymax) ? ymax : coord.ymax
+    xmin = coord.xmin === nothing ? xmin : coord.xmin
+    xmax = coord.xmax === nothing ? xmax : coord.xmax
+    ymin = coord.ymin === nothing ? ymin : coord.ymin
+    ymax = coord.ymax === nothing ? ymax : coord.ymax
 
-    if Gadfly.isnothing(xmin) || !isfinite(xmin)
+    if xmin === nothing || !isfinite(xmin)
         xmin = 0.0
         xmax = 1.0
     end
 
-    if Gadfly.isnothing(ymin) || !isfinite(ymin)
+    if ymin === nothing || !isfinite(ymin)
         ymin = 0.0
         ymax = 1.0
     end
diff --git a/src/data.jl b/src/data.jl
index 21fa375c7..4c63cae71 100644
--- a/src/data.jl
+++ b/src/data.jl
@@ -78,7 +78,7 @@ function show(io::IO, data::Data)
     maxlen = 0
     print(io, "Data(")
     for name in data_fields
-        if !isnothing(getfield(data, name))
+        if getfield(data, name) !== nothing
             print(io, "\n  ", string(name), "=")
             show(io, getfield(data, name))
         end
diff --git a/src/dataframes.jl b/src/dataframes.jl
index 2a7c6ddf3..eeb4e76ba 100644
--- a/src/dataframes.jl
+++ b/src/dataframes.jl
@@ -11,7 +11,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
     vm = um
     grouped_columns = Set{Symbol}()
     for colgroup in colgroups
-        if isnothing(colgroup.columns) # null => group all columns
+        if colgroup.columns === nothing # null => group all columns
             vm *= un
             grouped_columns = copy(allcolumns)
         else
@@ -34,7 +34,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
 
     # allocate vectors for grouped columns
     for (j, colgroup) in enumerate(colgroups)
-        cols = isnothing(colgroup.columns) ? allcolumns : colgroup.columns
+        cols = colgroup.columns === nothing ? allcolumns : colgroup.columns
 
         # figure the grouped common column type
         firstcol = U[first(cols)]
@@ -64,7 +64,7 @@ function meltdata(U::AbstractDataFrame, colgroups_::Vector{Col.GroupedColumn})
     col_indicators = Array{Symbol}(undef, vm, length(colgroups))
     row_indicators = Array{Int}(undef, vm, length(colgroups))
 
-    colidxs = [isnothing(colgroup.columns) ? collect(allcolumns) : colgroup.columns
+    colidxs = [colgroup.columns === nothing ? collect(allcolumns) : colgroup.columns
                for colgroup in colgroups]
 
     vi = 1
diff --git a/src/geom/bar.jl b/src/geom/bar.jl
index 6348072c2..697de3061 100644
--- a/src/geom/bar.jl
+++ b/src/geom/bar.jl
@@ -74,7 +74,7 @@ function render_bar(geom::BarGeometry,
             svgclass("geometry"))
     end
 
-    cs = isnothing(aes.color) ? theme.default_color : aes.color
+    cs = aes.color === nothing ? theme.default_color : aes.color
     compose!(ctx, fill(cs), svgclass("geometry"))
     if isa(theme.bar_highlight, Function)
         compose!(ctx, stroke(theme.bar_highlight(theme.default_color)))
@@ -272,7 +272,7 @@ function render(geom::BarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
         error("Orientation must be :horizontal or :vertical")
     end
 
-    if isnothing(aes.color)
+    if aes.color === nothing
         ctx = render_bar(geom, theme, aes, geom.orientation)
     elseif geom.position == :stack
         if geom.orientation == :horizontal
diff --git a/src/geom/boxplot.jl b/src/geom/boxplot.jl
index f47cb55eb..c56a8bcb4 100644
--- a/src/geom/boxplot.jl
+++ b/src/geom/boxplot.jl
@@ -123,7 +123,7 @@ function render(geom::BoxplotGeometry, theme::Gadfly.Theme, aes::Gadfly.Aestheti
         svgclass("geometry"))
 
     # Outliers
-    if !geom.suppress_outliers && !isnothing(aes.outliers) && !isempty(aes.outliers)
+    if !geom.suppress_outliers && aes.outliers !== nothing && !isempty(aes.outliers)
         xys = collect(Iterators.flatten(zip(cycle([x]), ys, cycle([c]))
                              for (x, ys, c) in zip(xs, aes.outliers, cs)))
         compose!(ctx, (context(),
@@ -133,7 +133,7 @@ function render(geom::BoxplotGeometry, theme::Gadfly.Theme, aes::Gadfly.Aestheti
     end
 
     # Middle
-    if !isnothing(aes.middle)
+    if aes.middle !== nothing
         compose!(ctx, (
            context(order=1),
            Compose.line([[(x - fw/2, mid), (x + fw/2, mid)]
diff --git a/src/geom/errorbar.jl b/src/geom/errorbar.jl
index 67ce96d30..2e5bfb4a0 100644
--- a/src/geom/errorbar.jl
+++ b/src/geom/errorbar.jl
@@ -110,7 +110,7 @@ function render(geom::YErrorBarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthe
         stroke([theme.stroke_color(c) for c in aes.color]),
         linewidth(theme.line_width))
 
-    (aes.color_key_continuous == true || isnothing(aes.color)) || compose!(ctx,
+    (aes.color_key_continuous == true || aes.color === nothing) || compose!(ctx,
             svgclass([svg_color_class_from_label(aes.color_label([c])[1]) for c in aes.color]))
 
     return ctx
@@ -148,7 +148,7 @@ function render(geom::XErrorBarGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthe
         stroke([theme.stroke_color(c) for c in aes.color]),
         linewidth(theme.line_width))
 
-    (aes.color_key_continuous == true || isnothing(aes.color)) || compose!(ctx,
+    (aes.color_key_continuous == true || aes.color === nothing) || compose!(ctx,
             svgclass([svg_color_class_from_label(aes.color_label([c])[1])
                       for c in aes.color]))
 
diff --git a/src/geom/hvabline.jl b/src/geom/hvabline.jl
index 69fa4968f..ca8e86000 100755
--- a/src/geom/hvabline.jl
+++ b/src/geom/hvabline.jl
@@ -18,7 +18,7 @@ struct HLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     HLineGeometry(color, size, style, tag) =
-            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 HLineGeometry(; color=nothing, size=nothing, style=nothing, tag=empty_tag) =
         HLineGeometry(color, size, style, tag)
@@ -36,9 +36,9 @@ element_aesthetics(::HLineGeometry) = [:yintercept]
 function render(geom::HLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("Geom.hline", aes, :yintercept)
 
-    color = isnothing(geom.color) ? theme.default_color : geom.color
-    size = isnothing(geom.size) ? theme.line_width : geom.size
-    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
+    color = geom.color === nothing ? theme.default_color : geom.color
+    size = geom.size === nothing ? theme.line_width : geom.size
+    style = geom.style === nothing ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.yintercept))
     size = check_arguments(size, length(aes.yintercept))
@@ -65,7 +65,7 @@ struct VLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     VLineGeometry(color, size, style, tag) =
-            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 VLineGeometry(; color=nothing, size=nothing, style=nothing, tag=empty_tag) =
         VLineGeometry(color, size, style, tag)
@@ -83,9 +83,9 @@ element_aesthetics(::VLineGeometry) = [:xintercept]
 function render(geom::VLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("Geom.vline", aes, :xintercept)
 
-    color = isnothing(geom.color) ? theme.default_color : geom.color
-    size = isnothing(geom.size) ? theme.line_width : geom.size
-    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
+    color = geom.color === nothing ? theme.default_color : geom.color
+    size = geom.size === nothing ? theme.line_width : geom.size
+    style = geom.style === nothing ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.xintercept))
     size = check_arguments(size, length(aes.xintercept))
@@ -112,7 +112,7 @@ struct ABLineGeometry <: Gadfly.GeometryElement
     tag::Symbol
 
     ABLineGeometry(color, size, style, tag) =
-            new(isnothing(color) ? nothing : Gadfly.parse_colorant(color), size, style, tag)
+            new(color === nothing ? nothing : Gadfly.parse_colorant(color), size, style, tag)
 end
 ABLineGeometry(; color=nothing, size=nothing, style=nothing, tag::Symbol=empty_tag) =
         ABLineGeometry(color, size, style, tag)
@@ -131,19 +131,19 @@ const abline = ABLineGeometry
 element_aesthetics(geom::ABLineGeometry) = [:intercept, :slope]
 
 function render(geom::ABLineGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
-    if isnothing(aes.intercept) && isnothing(aes.slope)
+    if aes.intercept === nothing && aes.slope === nothing
         aes.intercept = [0]
         aes.slope = [1]
-    elseif isnothing(aes.intercept)
+    elseif aes.intercept === nothing
         aes.intercept = fill(0,length(aes.slope))
-    elseif isnothing(aes.slope)
+    elseif aes.slope === nothing
         aes.slope = fill(1,length(aes.intercept))
     end
     Gadfly.assert_aesthetics_equal_length("Geom.line", aes, element_aesthetics(geom)...)
 
-    color = isnothing(geom.color) ? theme.default_color : geom.color
-    size = isnothing(geom.size) ? theme.line_width : geom.size
-    style = isnothing(geom.style) ? theme.line_style[1] : geom.style
+    color = geom.color === nothing ? theme.default_color : geom.color
+    size = geom.size === nothing ? theme.line_width : geom.size
+    style = geom.style === nothing ? theme.line_style[1] : geom.style
 
     color = check_arguments(color, length(aes.intercept))
     size = check_arguments(size, length(aes.intercept))
diff --git a/src/geom/label.jl b/src/geom/label.jl
index 48fca4d70..94a277c60 100644
--- a/src/geom/label.jl
+++ b/src/geom/label.jl
@@ -50,7 +50,7 @@ function deferred_label_context(geom::LabelGeometry,
 
     num_labels = length(aes.label)
 
-    if isnothing(aes.size)
+    if aes.size === nothing
         padding = fill(theme.point_size, num_labels) .+ theme.label_padding
     else
         padding = aes.size .+ theme.label_padding
@@ -279,7 +279,7 @@ function render(geom::LabelGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics
         end
 
         hpos, vpos, xoff, yoff = label_layouts[geom.position]
-        if isnothing(aes.size)
+        if aes.size === nothing
             offsets = [(xoff*(theme.point_size + theme.label_padding),
                         yoff*(theme.point_size + theme.label_padding))]
         else
diff --git a/src/geom/point.jl b/src/geom/point.jl
index beabffa94..a98e4fc95 100644
--- a/src/geom/point.jl
+++ b/src/geom/point.jl
@@ -67,7 +67,7 @@ function render(geom::PointGeometry, theme::Gadfly.Theme, aes::Gadfly.Aesthetics
     for (x, y, color, size, shape, alpha) in Compose.cyclezip(aes.x, aes.y, aes.color, aes.size, aes.shape, aes_alpha)
         shapefun = typeof(shape) <: Function ? shape : theme.point_shapes[shape]
         sizeval = typeof(size) <: Int ? interpolate_size(size) : size
-        strokecolor = !isnothing(aes.color_key_continuous) && aes.color_key_continuous ?
+        strokecolor = aes.color_key_continuous !== nothing && aes.color_key_continuous ?
                     theme.continuous_highlight_color(color) :
                     theme.discrete_highlight_color(color)
         class = svg_color_class_from_label(aes.color_label([color])[1])
diff --git a/src/geom/rectbin.jl b/src/geom/rectbin.jl
index b998fac0f..8a2ae0c81 100644
--- a/src/geom/rectbin.jl
+++ b/src/geom/rectbin.jl
@@ -94,7 +94,7 @@ function render(geom::RectangularBinGeometry, theme::Gadfly.Theme, aes::Gadfly.A
 
     allvisible = true
     for c in cs
-        if isnothing(c)
+        if c === nothing
             allvisible = false
             break
         end
diff --git a/src/geom/subplot.jl b/src/geom/subplot.jl
index a4c247780..abd4955f7 100644
--- a/src/geom/subplot.jl
+++ b/src/geom/subplot.jl
@@ -136,7 +136,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         inherited_aes = element_aesthetics(layer.geom)
         push!(inherited_aes, :xgroup, :ygroup)
         for var in inherited_aes
-            if isnothing(getfield(layer_aes, var))
+            if getfield(layer_aes, var) === nothing
                 setfield!(layer_aes, var, getfield(superplot_aes, var))
             end
         end
@@ -144,17 +144,17 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
  # z
     for (layer_data, layer_aes) in zip(subplot_layer_datas, subplot_layer_aess)
         z = getfield(layer_data, :z)
-        (!isnothing(z)) && setfield!(layer_aes, :z, z)
+        (z !== nothing) && setfield!(layer_aes, :z, z)
     end
 
     # work out the grid size
     m = 1
     n = 1
     for layer_aes in subplot_layer_aess
-        if !isnothing(layer_aes.xgroup)
+        if layer_aes.xgroup !== nothing
             m = max(m, maximum(layer_aes.xgroup))
         end
-        if !isnothing(layer_aes.ygroup)
+        if layer_aes.ygroup !== nothing
             n = max(n, maximum(layer_aes.ygroup))
         end
     end
@@ -315,7 +315,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         if i == n
             push!(guides, get(geom.guides, Guide.XTicks, Guide.xticks()))
 
-            if !isnothing(superplot_aes.xgroup)
+            if superplot_aes.xgroup !== nothing
                 push!(guides, get(geom.guides, Guide.XLabel, Guide.xlabel(xlabels[j])))
             end
         else
@@ -326,7 +326,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         if j == 1
             joff += 1
             push!(guides, get(geom.guides, Guide.YTicks, Guide.yticks()))
-            if !isnothing(superplot_aes.ygroup)
+            if superplot_aes.ygroup !== nothing
                 joff += 1
                 push!(guides, get(geom.guides, Guide.YLabel, Guide.ylabel(ylabels[i])))
             end
@@ -349,7 +349,7 @@ function render(geom::SubplotGrid, theme::Gadfly.Theme,
         # copy over the correct units, since we are reparenting the children
         for u in 1:size(subtbl, 1), v in 1:size(subtbl, 2)
             for child in subtbl[u, v]
-                if isnothing(child.units)
+                if child.units === nothing
                     child.units = subtbl.units
                 end
             end
diff --git a/src/geometry.jl b/src/geometry.jl
index 377bf07b3..125410f34 100644
--- a/src/geometry.jl
+++ b/src/geometry.jl
@@ -13,7 +13,7 @@ import Compose.combine # Prevent DataFrame.combine from taking over.
 import Gadfly: render, layers, element_aesthetics, inherit, escape_id,
                default_statistic, default_scales, element_coordinate_type,
                ScaleElement, svg_color_class_from_label, isconcrete,
-               concretize, discretize_make_ia, isnothing
+               concretize, discretize_make_ia
 import IterTools: distinct, takestrict
 import Compat.Iterators: cycle, product, repeated
 
diff --git a/src/guide.jl b/src/guide.jl
index 32162cbca..ab64e060f 100644
--- a/src/guide.jl
+++ b/src/guide.jl
@@ -9,7 +9,7 @@ using IterTools
 using JSON
 
 import Gadfly: render, escape_id, default_statistic, jsdata, jsplotdata,
-               svg_color_class_from_label, isnothing
+               svg_color_class_from_label
 
 
 # Where the guide should be placed in relation to the plot.
@@ -35,7 +35,7 @@ const questionmark = QuestionMark
 
 function render(guide::QuestionMark, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    text_color = isnothing(theme.background_color) ?
+    text_color = theme.background_color === nothing ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_box = compose!( context(),
         text(1w,0h+2px,"?",hright,vtop),
@@ -64,7 +64,7 @@ const helpscreen = HelpScreen
 
 function render(guide::HelpScreen, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    box_color = isnothing(theme.background_color) ?
+    box_color = theme.background_color === nothing ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_color = distinguishable_colors(2,box_color)[2]
     text_strings = ["h,j,k,l,arrows,drag to pan",
@@ -104,7 +104,7 @@ const crosshair = CrossHair
 
 function render(guide::CrossHair, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    text_color = isnothing(theme.background_color) ?
+    text_color = theme.background_color === nothing ?
             colorant"black" : distinguishable_colors(2,theme.background_color)[2]
     text_box = compose!(
         context(),
@@ -262,7 +262,7 @@ function render_discrete_color_key(colors::Vector{C},
                     fill(theme.key_label_color))
 
                 col = compose!(context(xpos, yoff), swatches, swatch_labels)
-                if !isnothing(aes_color_label)
+                if aes_color_label !== nothing
                     classes = [svg_color_class_from_label(aes_color_label([c])[1]) for c in cs]
                     #class_jscalls = ["data(\"color_class\", \"$(c)\")"
                                      #for c in classes]
@@ -395,7 +395,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
 
     (theme.key_position == :none || isempty(aes.color_key_colors)) && return PositionedGuide[]
     gpos = guide.pos
-    (theme.key_position == :inside && isnothing(gpos)) &&  (gpos = [0.7w, 0.25h])
+    (theme.key_position == :inside && gpos === nothing) &&  (gpos = [0.7w, 0.25h])
 
     used_colors = Set{Color}()
     colors = Array{Color}(undef, 0) # to preserve ordering
@@ -404,18 +404,18 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
     continuous_guide = false
     guide_title = guide.title
 
-    if isnothing(guide_title) && !isnothing(aes.color_key_title)
+    if guide_title === nothing && aes.color_key_title !== nothing
         guide_title = aes.color_key_title
     end
 
-    if !isnothing(aes.color_key_colors) &&
-       !isnothing(aes.color_key_continuous) &&
+    if aes.color_key_colors !== nothing &&
+       aes.color_key_continuous !== nothing &&
        aes.color_key_continuous
         continuous_guide = true
     end
 
     color_key_labels = aes.color_label(keys(aes.color_key_colors))
-    if !continuous_guide && !isnothing(guide.labels)
+    if !continuous_guide && guide.labels !== nothing
         color_key_labels = guide.labels
     end
 
@@ -430,7 +430,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
         end
     end
 
-    if isnothing(guide_title)
+    if guide_title === nothing
         guide_title = "Color"
     end
 
@@ -457,7 +457,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
                                          title_width, theme)
     end
 
-    if !isnothing(aes.shape)
+    if aes.shape !== nothing
         # TODO: Draw key for shapes. We need to think about how to make this
         # work. Do we need to optimize number of columns for shape and size
         # keys? I'm guessing it's not worth it.
@@ -469,7 +469,7 @@ function render(guide::ColorKey, theme::Gadfly.Theme,
     end
 
     position = right_guide_position
-    if !isnothing(gpos)
+    if gpos !== nothing
         position = over_guide_position
         ctxs = [compose(context(), (context(gpos[1],gpos[2]), ctxs[1]))]
     elseif theme.key_position == :left
@@ -517,11 +517,11 @@ function render(guide::ManualColorKey, theme::Gadfly.Theme,
 
     guide_title = guide.title
 
-    if isnothing(guide_title) && !isnothing(aes.color_key_title)
+    if guide_title === nothing && aes.color_key_title !== nothing
         guide_title = aes.color_key_title
     end
 
-    if isnothing(guide_title)
+    if guide_title === nothing
         guide_title = "Color"
     end
 
@@ -569,13 +569,13 @@ visibility.  `ticks` can also be an array of locations, or `nothing`.
 const xticks = XTicks
 
 default_statistic(guide::XTicks) =
-    isnothing(guide.ticks) ? Stat.identity() : Stat.xticks(ticks=guide.ticks)
+    guide.ticks === nothing ? Stat.identity() : Stat.xticks(ticks=guide.ticks)
 
 function render(guide::XTicks, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics, dynamic::Bool=true)
-    isnothing(guide.ticks) && return PositionedGuide[]
+    guide.ticks === nothing && return PositionedGuide[]
 
-    if !Gadfly.isnothing(aes.xtick)
+    if aes.xtick !== nothing
         ticks = aes.xtick
         tickvisibility = aes.xtickvisible
         scale = aes.xtickscale
@@ -592,7 +592,7 @@ function render(guide::XTicks, theme::Gadfly.Theme,
         scale = Any[]
     end
 
-    if !Gadfly.isnothing(aes.xgrid)
+    if aes.xgrid !== nothing
         grids = aes.xgrid
         gridvisibility = length(grids) < length(ticks) ?  tickvisibility[2:end] : tickvisibility
     else
@@ -740,7 +740,7 @@ visibility.  `ticks` can also be an array of locations, or `nothing`.
 const yticks = YTicks
 
 function default_statistic(guide::YTicks)
-    if isnothing(guide.ticks)
+    if guide.ticks === nothing
         return Stat.identity()
     else
         return Stat.yticks(ticks=guide.ticks)
@@ -749,11 +749,11 @@ end
 
 function render(guide::YTicks, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics, dynamic::Bool=true)
-    if isnothing(guide.ticks)
+    if guide.ticks === nothing
         return PositionedGuide[]
     end
 
-    if !Gadfly.isnothing(aes.ytick)
+    if aes.ytick !== nothing
         ticks = aes.ytick
         tickvisibility = aes.ytickvisible
         scale = aes.ytickscale
@@ -769,7 +769,7 @@ function render(guide::YTicks, theme::Gadfly.Theme,
         scale = Any[]
     end
 
-    if !Gadfly.isnothing(aes.ygrid)
+    if aes.ygrid !== nothing
         grids = aes.ygrid
         if length(grids) < length(ticks)
             gridvisibility = tickvisibility[2:end]
@@ -919,7 +919,7 @@ const xlabel = XLabel
 
 function render(guide::XLabel, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    if isnothing(guide.label) || isempty(guide.label)
+    if guide.label === nothing || isempty(guide.label)
         return nothing
     end
 
@@ -986,7 +986,7 @@ const ylabel = YLabel
 
 
 function render(guide::YLabel, theme::Gadfly.Theme, aes::Gadfly.Aesthetics)
-    if isnothing(guide.label) || isempty(guide.label)
+    if guide.label === nothing || isempty(guide.label)
         return nothing
     end
 
@@ -1044,7 +1044,7 @@ const title = Title
 
 function render(guide::Title, theme::Gadfly.Theme,
                 aes::Gadfly.Aesthetics)
-    if isnothing(guide.label) || isempty(guide.label)
+    if guide.label === nothing || isempty(guide.label)
         return nothing
     end
 
@@ -1160,9 +1160,9 @@ function layout_guides(plot_context::Context,
     aspect_ratio = nothing
     if isa(coord, Gadfly.Coord.cartesian)
         if coord.fixed
-            aspect_ratio = isnothing(plot_context.units) ? 1.0 :
+            aspect_ratio = (plot_context.units === nothing) ? 1.0 :
                 abs(plot_context.units.width / plot_context.units.height)
-        elseif !isnothing(coord.aspect_ratio)
+        elseif coord.aspect_ratio !== nothing
             aspect_ratio = coord.aspect_ratio
         end
     end
@@ -1172,7 +1172,7 @@ function layout_guides(plot_context::Context,
     i = 1
     for (ctxs, order) in guides[top_guide_position]
         for ctx in ctxs
-            if isnothing(ctx.units) && !isnothing(plot_units)
+            if ctx.units === nothing && plot_units !== nothing
                 ctx.units = UnitBox(plot_units, toppad=0mm, bottompad=0mm)
             end
         end
@@ -1183,7 +1183,7 @@ function layout_guides(plot_context::Context,
     i += 1
     for (ctxs, order) in guides[bottom_guide_position]
         for ctx in ctxs
-            if isnothing(ctx.units) && !isnothing(plot_units)
+            if ctx.units === nothing && plot_units !== nothing
                 ctx.units = UnitBox(plot_units, toppad=0mm, bottompad=0mm)
             end
         end
@@ -1195,7 +1195,7 @@ function layout_guides(plot_context::Context,
     j = 1
     for (ctxs, order) in guides[left_guide_position]
         for ctx in ctxs
-            if isnothing(ctx.units) && !isnothing(plot_units)
+            if ctx.units === nothing && plot_units !== nothing
                 ctx.units = UnitBox(plot_units, leftpad=0mm, rightpad=0mm)
             end
         end
@@ -1206,7 +1206,7 @@ function layout_guides(plot_context::Context,
     j += 1
     for (ctxs, order) in guides[right_guide_position]
         for ctx in ctxs
-            if isnothing(ctx.units) && !isnothing(plot_units)
+            if ctx.units === nothing && plot_units !== nothing
                 ctx.units = UnitBox(plot_units, leftpad=0mm, rightpad=0mm)
             end
         end
diff --git a/src/guide/keys.jl b/src/guide/keys.jl
index d9d9d77b2..f62568d00 100644
--- a/src/guide/keys.jl
+++ b/src/guide/keys.jl
@@ -32,11 +32,11 @@ function Guide.render(guide::Guide.ShapeKey, theme::Gadfly.Theme, aes::Gadfly.Ae
 
     # Aesthetics for keys: shape_key_title, shape_label (Function), shape_key_shapes (AbstractDict)    
     nshapes = length(unique(aes.shape))
-    guide_title = (guide.title!="Shape" || isnothing(aes.shape_key_title)) ? guide.title : aes.shape_key_title
+    guide_title = (guide.title!="Shape" || aes.shape_key_title === nothing) ? guide.title : aes.shape_key_title
     shape_key_labels = !(guide.labels==[""]) ? guide.labels : aes.shape_label(1:nshapes)
     
     colors = [nothing]
-    if !isnothing(aes.shape_key_title)  && (aes.color_key_title==aes.shape_key_title)
+    if aes.shape_key_title !== nothing  && (aes.color_key_title==aes.shape_key_title)
         colors = collect(keys(aes.color_key_colors))
     end
     
@@ -70,8 +70,8 @@ function render_discrete_key(labels::Vector{String}, title_ctx::Context, title_w
 
     n = max(length(colors), length(shapes))
     shape1 = shapes[1]
-    shapes = isnothing(shape1) ? fill(theme.key_swatch_shape, n) : theme.point_shapes[shapes]
-    (isnothing(colors[1])) && (colors = fill((isnothing(theme.key_swatch_color)) ? theme.default_color : theme.key_swatch_color, n))
+    shapes = shape1 === nothing ? fill(theme.key_swatch_shape, n) : theme.point_shapes[shapes]
+    (colors[1] === nothing) && (colors = fill((theme.key_swatch_color === nothing) ? theme.default_color : theme.key_swatch_color, n))
 
     # only consider layouts with a reasonable number of columns
     maxcols = theme.key_max_columns < 1 ? 1 : theme.key_max_columns
@@ -144,7 +144,7 @@ function render_discrete_key(labels::Vector{String}, title_ctx::Context, title_w
                     fill(theme.key_label_color))
 
                 col = compose!(context(xpos, yoff), swatches, swatch_labels)
-                if !isnothing(aes_color_label)
+                if aes_color_label !== nothing
                     classes = [svg_color_class_from_label(aes_color_label([c])[1]) for c in clrs]
                     #class_jscalls = ["data(\"color_class\", \"$(c)\")" for c in classes]
                     compose!(col,
diff --git a/src/mapping.jl b/src/mapping.jl
index 9a7d9cc1b..072f76696 100644
--- a/src/mapping.jl
+++ b/src/mapping.jl
@@ -87,7 +87,7 @@ end
 function meltdata(U::AbstractVector, colgroups_::Vector{Col.GroupedColumn})
     colgroups = Set(colgroups_)
 
-    if length(colgroups) != 1 || !isnothing(first(colgroups).columns)
+    if length(colgroups) != 1 || first(colgroups).columns !== nothing
         # if every column is of the same length, treat it as a matrix
         if length(Set([length(u for u in U)])) == 1
             return meltdata(cat(U..., dims=2), colgroups_)
@@ -130,7 +130,7 @@ function meltdata(U::AbstractMatrix, colgroups_::Vector{Col.GroupedColumn})
     vm = um
     grouped_columns = BitSet()
     for colgroup in colgroups
-        if isnothing(colgroup.columns)
+        if colgroup.columns === nothing
             vm *= un
             grouped_columns = copy(allcolumns)
         else
@@ -149,7 +149,7 @@ function meltdata(U::AbstractMatrix, colgroups_::Vector{Col.GroupedColumn})
     col_indicators = Array{Int}(undef, vm, length(colgroups))
     row_indicators = Array{Int}(undef, vm, length(colgroups))
 
-    colidxs = [isnothing(colgroup.columns) ? collect(allcolumns) : colgroup.columns
+    colidxs = [colgroup.columns === nothing ? collect(allcolumns) : colgroup.columns
                for colgroup in colgroups]
 
     vi = 1
diff --git a/src/misc.jl b/src/misc.jl
index 5ddbcd80a..b1583a9f8 100644
--- a/src/misc.jl
+++ b/src/misc.jl
@@ -178,7 +178,7 @@ function inherit!(a::T, b::T) where T
         aval = getfield(a, field)
         bval = getfield(b, field)
         # TODO: this is a hack to let non-default labelers overide the defaults
-        if isnothing(aval) || aval === string || aval == showoff
+        if aval === nothing || aval === string || aval == showoff
             setfield!(a, field, bval)
         elseif typeof(aval) <: Dict && typeof(bval) <: Dict
             merge!(aval, getfield(b, field))
diff --git a/src/scale.jl b/src/scale.jl
index a87692074..555806bc6 100644
--- a/src/scale.jl
+++ b/src/scale.jl
@@ -11,7 +11,7 @@ using CategoricalArrays
 using Printf
 
 import Gadfly: element_aesthetics, isconcrete, concrete_length, discretize_make_ia,
-    aes2str, valid_aesthetics, isnothing
+    aes2str, valid_aesthetics
 import Distributions: Distribution
 
 include("color_misc.jl")
@@ -86,7 +86,7 @@ struct ContinuousScale <: Gadfly.ScaleElement
     function ContinuousScale(vars, trans,
                              minvalue, maxvalue, minticks, maxticks,
                              labels, format, scalable)
-        !isnothing(minvalue) && !isnothing(maxvalue) && minvalue > maxvalue &&
+        minvalue !== nothing && maxvalue !== nothing && minvalue > maxvalue &&
                 error("Cannot construct a ContinuousScale with minvalue > maxvalue")
         new(vars, trans, minvalue, maxvalue, minticks, maxticks, labels, format, scalable)
     end
@@ -100,9 +100,9 @@ function ContinuousScale(vars, trans;
 end
 
 function make_labeler(scale::ContinuousScale)
-    if !isnothing(scale.labels)
+    if scale.labels !== nothing
         xs -> [scale.labels(x) for x in xs]
-    elseif isnothing(scale.format)
+    elseif scale.format === nothing
         scale.trans.label
     else
         xs -> scale.trans.label(xs, scale.format)
@@ -190,7 +190,7 @@ function apply_scale(scale::ContinuousScale,
             if vals isa CategoricalArray
                 throw(ArgumentError("continuous scale for $var aesthetic when stored as a CategoricalArray. Consider using a discrete scale or convert data to an Array."))
             end
-            isnothing(vals) && continue
+            vals === nothing && continue
 
             # special case for function arrays bound to :y
             # pass the function values through and wait for the scale to
@@ -245,7 +245,7 @@ function apply_scale(scale::ContinuousScale,
             end
         end
 
-        if !isnothing(scale.minvalue)
+        if scale.minvalue !== nothing
             if scale.vars === x_vars
                 aes.xviewmin = scale.trans.f(scale.minvalue)
             elseif scale.vars === y_vars
@@ -253,7 +253,7 @@ function apply_scale(scale::ContinuousScale,
             end
         end
 
-        if !isnothing(scale.maxvalue)
+        if scale.maxvalue !== nothing
             if scale.vars === x_vars
                 aes.xviewmax = scale.trans.f(scale.maxvalue)
             elseif scale.vars === y_vars
@@ -272,7 +272,7 @@ end
 
 
 function discretize(values, levels=nothing, order=nothing, preserve_order=true)
-    if isnothing(levels)
+    if levels === nothing
         if preserve_order
             levels = OrderedSet()
             for value in values
@@ -286,7 +286,7 @@ function discretize(values, levels=nothing, order=nothing, preserve_order=true)
         da = discretize_make_ia(values, levels)
     end
 
-    if !isnothing(order)
+    if order !== nothing
         return discretize_make_ia(da, da.values[order])
     else
         return da
@@ -370,13 +370,13 @@ function apply_scale(scale::DiscreteScale, aess::Vector{Gadfly.Aesthetics}, data
     for (aes, data) in zip(aess, datas)
         for var in scale.vars
             label_var = Symbol(var, "_label")
-            isnothing(getfield(data, var)) && continue
+            getfield(data, var) === nothing && continue
 
             disc_data = discretize(getfield(data, var), scale.levels, scale.order)
             setfield!(aes, var, discretize_make_ia(Int64.(disc_data.index)))
 
             # The leveler for discrete scales is a closure over the discretized data.
-            if isnothing(scale.labels)
+            if scale.labels === nothing
                 function default_labeler(xs)
                     lvls = filter(!ismissing, disc_data.values)
                     vals = Any[1 <= x <= length(lvls) ? lvls[x] : "" for x in xs]
@@ -435,7 +435,7 @@ element_aesthetics(scale::IdentityColorScale) = [:color]
 function apply_scale(scale::IdentityColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        isnothing(data.color) && continue
+        data.color === nothing && continue
         aes.color = discretize_make_ia(data.color)
         aes.color_key_colors = Dict()
     end
@@ -519,7 +519,7 @@ function apply_scale(scale::DiscreteColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     levelset = OrderedSet()
     for (aes, data) in zip(aess, datas)
-        isnothing(data.color) && continue
+        data.color === nothing && continue
         for d in data.color
             # Remove missing values
             # FixMe! The handling of missing values shouldn't be this scattered across the source
@@ -527,13 +527,13 @@ function apply_scale(scale::DiscreteColorScale,
         end
     end
 
-    if isnothing(scale.levels)
+    if scale.levels === nothing
         scale_levels = [levelset...]
         scale.preserve_order || sort!(scale_levels)
     else
         scale_levels = scale.levels
     end
-    isnothing(scale.order) || permute!(scale_levels, scale.order)
+    scale.order === nothing || permute!(scale_levels, scale.order)
     colors = convert(Vector{RGB{Float32}}, scale.f(length(scale_levels)))
 
     color_map = Dict([(color, string(label))
@@ -541,7 +541,7 @@ function apply_scale(scale::DiscreteColorScale,
     labeler(xs) = [color_map[x] for x in xs]
 
     for (aes, data) in zip(aess, datas)
-        isnothing(data.color) && continue
+        data.color === nothing && continue
         # Remove missing values
         # FixMe! The handling of missing values shouldn't be this scattered across the source
         ds = discretize([c for c in data.color if !ismissing(c)], scale_levels)
@@ -625,7 +625,7 @@ const color_continuous_gradient = color_continuous  ### WHY HAVE THIS ALIAS?
 
 function apply_scale(scale::ContinuousColorScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
-    cdata = skipmissing(Iterators.flatten(i.color for i in datas if !isnothing(i.color)))
+    cdata = skipmissing(Iterators.flatten(i.color for i in datas if i.color !== nothing))
     if !isempty(cdata)
       cmin, cmax = extrema(cdata)
     else
@@ -633,9 +633,9 @@ function apply_scale(scale::ContinuousColorScale,
     end
 
     strict_span = false
-    !isnothing(scale.minvalue) && !isnothing(scale.maxvalue) && (strict_span=true)
-    !isnothing(scale.minvalue) && (cmin=scale.minvalue)
-    !isnothing(scale.maxvalue) && (cmax=scale.maxvalue)
+    scale.minvalue !== nothing && scale.maxvalue !== nothing && (strict_span=true)
+    scale.minvalue !== nothing && (cmin=scale.minvalue)
+    scale.maxvalue !== nothing && (cmax=scale.maxvalue)
 
     cmin, cmax = promote(cmin, cmax)
 
@@ -649,7 +649,7 @@ function apply_scale(scale::ContinuousColorScale,
     cspan = cmax != cmin ? cmax - cmin : 1.0
 
     for (aes, data) in zip(aess, datas)
-        isnothing(data.color) && continue
+        data.color === nothing && continue
 
         aes.color = Array{RGB{Float32}}(undef, length(data.color))
         apply_scale_typed!(aes.color, data.color, scale, cmin, cspan)
@@ -698,7 +698,7 @@ end
 function apply_scale(scale::LabelScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        isnothing(data.label) && continue
+        data.label === nothing && continue
         aes.label = discretize(data.label)
     end
 end
@@ -738,7 +738,7 @@ element_aesthetics(scale::IdentityScale) = [scale.var]
 function apply_scale(scale::IdentityScale,
                      aess::Vector{Gadfly.Aesthetics}, datas::Vector{Gadfly.Data})
     for (aes, data) in zip(aess, datas)
-        isnothing(getfield(data, scale.var)) && continue
+        getfield(data, scale.var) === nothing && continue
         setfield!(aes, scale.var, getfield(data, scale.var))
     end
 end
diff --git a/src/statistics.jl b/src/statistics.jl
index 6a2769d35..49ad28a88 100644
--- a/src/statistics.jl
+++ b/src/statistics.jl
@@ -17,8 +17,7 @@ using LinearAlgebra
 using Random
 
 import Gadfly: Scale, Coord, input_aesthetics, output_aesthetics,
-    default_scales, isconcrete, setfield!, discretize_make_ia, aes2str,
-    isnothing
+    default_scales, isconcrete, setfield!, discretize_make_ia, aes2str
 import KernelDensity
 # import Distributions: Uniform, Distribution, qqbuild
 import IterTools: distinct
@@ -187,7 +186,7 @@ function apply_statistic(stat::BarStatistic,
 
     iscontinuous = haskey(scales, var) && isa(scales[var], Scale.ContinuousScale)
 
-    if isnothing(getfield(aes, minvar)) || isnothing(getfield(aes, maxvar))
+    if getfield(aes, minvar) === nothing || getfield(aes, maxvar) === nothing
         minvals, maxvals = barminmax(vals, iscontinuous)
 
         setfield!(aes, minvar, minvals)
@@ -195,13 +194,13 @@ function apply_statistic(stat::BarStatistic,
     end
 
     z = zero(eltype(getfield(aes, othervar)))
-    if isnothing(getfield(aes, viewminvar)) && z < minimum(getfield(aes, othervar))
+    if getfield(aes, viewminvar) === nothing && z < minimum(getfield(aes, othervar))
         setfield!(aes, viewminvar, z)
-    elseif isnothing(getfield(aes, viewmaxvar)) && z > maximum(getfield(aes, othervar))
+    elseif getfield(aes, viewmaxvar) === nothing && z > maximum(getfield(aes, othervar))
         setfield!(aes, viewmaxvar, z)
     end
 
-    if stat.position == :stack && !isnothing(aes.color)
+    if stat.position == :stack && aes.color !== nothing
         groups = Dict{Any,Float64}()
         for (x, y) in zip(getfield(aes, othervar), vals)
             Gadfly.isconcrete(x) || continue
@@ -215,11 +214,11 @@ function apply_statistic(stat::BarStatistic,
 
         viewmin, viewmax = extrema(values(groups))
         aes_viewminvar = getfield(aes, viewminvar)
-        if isnothing(aes_viewminvar) || aes_viewminvar > viewmin
+        if aes_viewminvar === nothing || aes_viewminvar > viewmin
             setfield!(aes, viewminvar, viewmin)
         end
         aes_viewmaxvar = getfield(aes, viewmaxvar)
-        if isnothing(aes_viewmaxvar) || aes_viewmaxvar < viewmax
+        if aes_viewmaxvar === nothing || aes_viewmaxvar < viewmax
             setfield!(aes, viewmaxvar, viewmax)
         end
     end
@@ -250,7 +249,7 @@ function HistogramStatistic(; bincount=nothing,
                               orientation=:vertical,
                               density=false,
                               limits=NamedTuple())
-    if !isnothing(bincount)
+    if bincount !== nothing
         HistogramStatistic(bincount, bincount, position, orientation, density, limits)
     else
         HistogramStatistic(minbincount, maxbincount, position, orientation, density, limits)
@@ -341,7 +340,7 @@ function apply_statistic(stat::HistogramStatistic,
 
     stat.density && (bincounts = bincounts ./ (sum(bincounts) * binwidth))
 
-    if isnothing(aes.color)
+    if aes.color === nothing
         T = typeof(x_min + 1*binwidth)
         setfield!(aes, othervar, Array{Float64}(undef, d))
         setfield!(aes, minvar, Array{T}(undef, d))
@@ -399,7 +398,7 @@ function apply_statistic(stat::HistogramStatistic,
         if stat.position == :stack
             viewmax = Float64(maximum(stack_height))
             aes_viewmax = getfield(aes, viewmaxvar)
-            if isnothing(aes_viewmax) || aes_viewmax < viewmax
+            if aes_viewmax === nothing || aes_viewmax < viewmax
                 setfield!(aes, viewmaxvar, viewmax)
             end
         end
@@ -407,7 +406,7 @@ function apply_statistic(stat::HistogramStatistic,
         aes.color = discretize_make_ia(colors)
     end
 
-    isnothing(getfield(aes, viewminvar)) && setfield!(aes, viewminvar, 0.0)
+    getfield(aes, viewminvar) === nothing && setfield!(aes, viewminvar, 0.0)
 
     if haskey(scales, othervar)
         data = Gadfly.Data()
@@ -418,7 +417,7 @@ function apply_statistic(stat::HistogramStatistic,
         # See issue #560. Stacked histograms on a non-linear y scale are a strange
         # thing. After some discussion, the least confusing thing is to make the stack
         # partitioned linearly. Here we make that adjustment.
-        if stat.position == :stack && !isnothing(aes.color)
+        if stat.position == :stack && aes.color !== nothing
             # A little trickery to figure out the scale stack height.
             data = Gadfly.Data()
             setfield!(data, othervar, stack_height)
@@ -512,7 +511,7 @@ function apply_statistic(stat::DensityStatistic,
                          aes::Gadfly.Aesthetics)
     Gadfly.assert_aesthetics_defined("DensityStatistic", aes, :x)
 
-    if isnothing(aes.color)
+    if aes.color === nothing
         isa(aes.x[1], Real) || error("Kernel density estimation only works on Real types.")
 
         x_f64 = collect(Float64, aes.x)
@@ -562,12 +561,12 @@ function Histogram2DStatistic(; xbincount=nothing,
                                 ybincount=nothing,
                                 yminbincount=3,
                                 ymaxbincount=150)
-    if !isnothing(xbincount)
+    if xbincount !== nothing
         xminbincount = xbincount
         xmaxbincount = xbincount
     end
 
-    if !isnothing(ybincount)
+    if ybincount !== nothing
         yminbincount = ybincount
         ymaxbincount = ybincount
     end
@@ -771,7 +770,7 @@ function apply_statistic(stat::TickStatistic,
             error("TickStatistic cannot be applied to subplot coordinates.")
 
     # don't clobber existing ticks
-    isnothing(getfield(aes, Symbol(stat.axis, "tick"))) || return
+    getfield(aes, Symbol(stat.axis, "tick")) === nothing || return
 
     in_group_var = Symbol(stat.axis, "group")
     minval, maxval = nothing, nothing
@@ -782,11 +781,11 @@ function apply_statistic(stat::TickStatistic,
     for var in in_vars
         categorical && !in(var,[:x,:y]) && continue
         vals = getfield(aes, var)
-        if !isnothing(vals) && eltype(vals) != Function
-            if isnothing(minval)
+        if vals !== nothing && eltype(vals) != Function
+            if minval === nothing
                 minval = first(vals)
             end
-            if isnothing(maxval)
+            if maxval === nothing
                 maxval = first(vals)
             end
             T = promote_type(typeof(minval), typeof(maxval))
@@ -795,14 +794,14 @@ function apply_statistic(stat::TickStatistic,
             maxval = convert(T, maxval)
 
             if stat.axis == "x"
-                dsize = isnothing(aes.xsize) ? [nothing] : aes.xsize
+                dsize = aes.xsize === nothing ? [nothing] : aes.xsize
             elseif stat.axis == "y"
-                dsize = isnothing(aes.ysize) ? [nothing] : aes.ysize
+                dsize = aes.ysize === nothing ? [nothing] : aes.ysize
             else
                 dsize = [nothing]
             end
 
-            size = isnothing(aes.size) ? [nothing] : aes.size
+            size = aes.size === nothing ? [nothing] : aes.size
 
             minval, maxval = apply_statistic_typed(minval, maxval, vals, size, dsize)
             push!(in_vals, vals)
@@ -825,17 +824,17 @@ function apply_statistic(stat::TickStatistic,
 
     # check the x/yviewmin/max pesudo-aesthetics
     if stat.axis == "x"
-        if !isnothing(aes.xviewmin)
+        if aes.xviewmin !== nothing
             minval = min(minval, aes.xviewmin)
         end
-        if !isnothing(aes.xviewmax)
+        if aes.xviewmax !== nothing
             maxval = max(maxval, aes.xviewmax)
         end
     elseif stat.axis == "y"
-        if !isnothing(aes.yviewmin)
+        if aes.yviewmin !== nothing
             minval = min(minval, aes.yviewmin)
         end
-        if !isnothing(aes.yviewmax)
+        if aes.yviewmax !== nothing
             maxval = max(maxval, aes.yviewmax)
         end
     end
@@ -844,20 +843,20 @@ function apply_statistic(stat::TickStatistic,
     strict_span = false
     if typeof(coord) == Coord.Cartesian
         if stat.axis == "x"
-            if !isnothing(coord.xmin)
+            if coord.xmin !== nothing
                 minval = coord.xmin
                 strict_span = true
             end
-            if !isnothing(coord.xmax)
+            if coord.xmax !== nothing
                 maxval = coord.xmax
                 strict_span = true
             end
         elseif stat.axis == "y"
-            if !isnothing(coord.ymin)
+            if coord.ymin !== nothing
                 minval = coord.ymin
                 strict_span = true
             end
-            if !isnothing(coord.ymax)
+            if coord.ymax !== nothing
                 maxval = coord.ymax
                 strict_span = true
             end
@@ -924,12 +923,12 @@ function apply_statistic(stat::TickStatistic,
     setfield!(aes, Symbol(stat.axis, "tickscale"), tickscale)
 
     viewmin_var = Symbol(stat.axis, "viewmin")
-    if isnothing(getfield(aes, viewmin_var)) || getfield(aes, viewmin_var) > viewmin
+    if getfield(aes, viewmin_var) === nothing || getfield(aes, viewmin_var) > viewmin
         setfield!(aes, viewmin_var, viewmin)
     end
 
     viewmax_var = Symbol(stat.axis, "viewmax")
-    if isnothing(getfield(aes, viewmax_var)) || getfield(aes, viewmax_var) < viewmax
+    if getfield(aes, viewmax_var) === nothing || getfield(aes, viewmax_var) < viewmax
         setfield!(aes, viewmax_var, viewmax)
     end
 
@@ -960,12 +959,12 @@ function minvalmaxval(minval::T, maxval::T, val, s, ds) where T
         maxval = val
     end
 
-    if !isnothing(s) && typeof(s) <: AbstractFloat
+    if s !== nothing && typeof(s) <: AbstractFloat
         minval = min(minval, val - s)::T
         maxval = max(maxval, val + s)::T
     end
 
-    if !isnothing(ds)
+    if ds !== nothing
         minval = min(minval, val - ds)::T
         maxval = max(maxval, val + ds)::T
     end
@@ -1000,7 +999,7 @@ function apply_statistic(stat::BoxplotStatistic,
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
 
-    xflag = !isnothing(aes.x)
+    xflag = aes.x !== nothing
     aes_x = (xflag ? eltype(aes.x) : Int)[]
     if xflag
         aes_x = aes.x
@@ -1008,26 +1007,26 @@ function apply_statistic(stat::BoxplotStatistic,
         aes_x = ones(Int, length(aes.y))
         aes.x_label = x -> fill("", length(x))
     end
-    colorflag = !isnothing(aes.color)
+    colorflag = aes.color !== nothing
     aes_color =  colorflag ? aes.color : fill(nothing, length(aes_x))
                      
-    if isnothing(aes.y)
+    if aes.y === nothing
         groups = Any[]
         for (x, c) in zip(aes.x, cycle(aes_color))
             push!(groups, (x, c))
         end
 
         yviewmin, yviewmax = minimum(aes.lower_fence), maximum(aes.upper_fence)
-        if !isnothing(aes.outliers)
+        if aes.outliers !== nothing
             yviewmin = minimum(yviewmin, aes.outliers)
             yviewmax = maximum(yviewmax, aes.outliers)
         end
 
-        if isnothing(aes.yviewmin) || aes.yviewmin > yviewmin
+        if aes.yviewmin === nothing || aes.yviewmin > yviewmin
             aes.yviewmin = yviewmin
         end
 
-        if isnothing(aes.yviewmax) || aes.yviewmax < yviewmax
+        if aes.yviewmax === nothing || aes.yviewmax < yviewmax
             aes.yviewmax = yviewmax
         end
     else
@@ -1083,11 +1082,11 @@ function apply_statistic(stat::BoxplotStatistic,
         xviewmin = xmin - minspan / 2
         xviewmax = xmax + minspan / 2
 
-        if isnothing(aes.xviewmin) || aes.xviewmin > xviewmin
+        if aes.xviewmin === nothing || aes.xviewmin > xviewmin
             aes.xviewmin = xviewmin
         end
 
-        if isnothing(aes.xviewmax) || aes.xviewmax < xviewmax
+        if aes.xviewmax === nothing || aes.xviewmax < xviewmax
             aes.xviewmax = xviewmax
         end
     end
@@ -1151,7 +1150,7 @@ function Stat.apply_statistic(stat::SmoothStatistic,
         error("Stat.loess and Stat.lm require that x and y be bound to arrays of plain numbers.")
     end
 
-    colorflag = !isnothing(aes.color)
+    colorflag = aes.color !== nothing
     aes_color =  colorflag ? aes.color : fill(nothing, length(aes.x))
 
     uc = unique(aes_color)
@@ -1309,18 +1308,18 @@ function apply_statistic(stat::StepStatistic,
     p = sortperm(aes.x, alg=MergeSort)
     permute!(aes.x, p)
     permute!(aes.y, p)
-    !isnothing(aes.group) && permute!(aes.group, p)
-    !isnothing(aes.color) && permute!(aes.color, p)
+    aes.group !== nothing && permute!(aes.group, p)
+    aes.color !== nothing && permute!(aes.color, p)
 
-    if !isnothing(aes.group)
+    if aes.group !== nothing
         Gadfly.assert_aesthetics_equal_length("StepStatistic", aes, :x, :group)
         permute!(aes.x, p)
         permute!(aes.y, p)
         permute!(aes.group, p)
-        !isnothing(aes.color) && permute!(aes.color, p)
+        aes.color !== nothing && permute!(aes.color, p)
     end
 
-    if !isnothing(aes.color)
+    if aes.color !== nothing
         Gadfly.assert_aesthetics_equal_length("StepStatistic", aes, :x, :color)
         # TODO: use this when we switch to 0.4
         # sortperm!(p, aes.color, alg=MergeSort, lt=Gadfly.color_isless)
@@ -1328,13 +1327,13 @@ function apply_statistic(stat::StepStatistic,
         permute!(aes.x, p)
         permute!(aes.y, p)
         permute!(aes.color, p)
-        !isnothing(aes.group) && permute!(aes.group, p)
+        aes.group !== nothing && permute!(aes.group, p)
     end
 
     x_step = Array{eltype(aes.x)}(undef, 0)
     y_step = Array{eltype(aes.y)}(undef, 0)
-    color_step = isnothing(aes.color) ? nothing : Array{eltype(aes.color)}(undef, 0)
-    group_step = isnothing(aes.group) ? nothing : Array{eltype(aes.group)}(undef, 0)
+    color_step = aes.color === nothing ? nothing : Array{eltype(aes.color)}(undef, 0)
+    group_step = aes.group === nothing ? nothing : Array{eltype(aes.group)}(undef, 0)
 
     i = 1
     i_offset = 1
@@ -1344,17 +1343,17 @@ function apply_statistic(stat::StepStatistic,
 
         (u > length(aes.x) || v > length(aes.y)) && break
 
-        if (!isnothing(aes.color) &&
+        if (aes.color !== nothing &&
              (aes.color[u] != aes.color[i_offset] || aes.color[v] != aes.color[i_offset])) ||
-           (!isnothing(aes.group) &&
+           (aes.group !== nothing &&
              (aes.group[u] != aes.color[i_offset] || aes.color[v] != aes.group[i_offset]))
             i_offset = max(u, v)
             i = 1
         else
             push!(x_step, aes.x[u])
             push!(y_step, aes.y[v])
-            !isnothing(aes.color) && push!(color_step, aes.color[i_offset])
-            !isnothing(aes.group) && push!(group_step, aes.group[i_offset])
+            aes.color !== nothing && push!(color_step, aes.color[i_offset])
+            aes.group !== nothing && push!(group_step, aes.group[i_offset])
             i += 1
         end
     end
@@ -1406,7 +1405,7 @@ function apply_statistic(stat::FunctionStatistic,
     end
 
     # color was bound explicitly
-    if !isnothing(aes.color)
+    if aes.color !== nothing
         func_color = aes.color
         aes.color = Array{eltype(aes.color)}(undef, length(aes.y) * stat.num_samples)
         groups = Array{Int}(undef, length(aes.y) * stat.num_samples)
@@ -1466,15 +1465,15 @@ function apply_statistic(stat::ContourStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    xs = isnothing(aes.x) ? nothing : convert(Vector{Float64}, aes.x)
-    ys = isnothing(aes.y) ? nothing : convert(Vector{Float64}, aes.y)
+    xs = aes.x === nothing ? nothing : convert(Vector{Float64}, aes.x)
+    ys = aes.y === nothing ? nothing : convert(Vector{Float64}, aes.y)
 
     if typeof(aes.z) <: Function
-        if isnothing(xs) && !isnothing(aes.xmin) && !isnothing(aes.xmax)
+        if xs === nothing && aes.xmin !== nothing && aes.xmax !== nothing
             xs = range(aes.xmin[1], stop=aes.xmax[1], length=stat.samples)
         end
 
-        if isnothing(ys) && !isnothing(aes.ymin) && !isnothing(aes.ymax)
+        if ys === nothing && aes.ymin !== nothing && aes.ymax !== nothing
             ys = range(aes.ymin[1], stop=aes.ymax[1], length=stat.samples)
         end
 
@@ -1483,10 +1482,10 @@ function apply_statistic(stat::ContourStatistic,
     elseif typeof(aes.z) <: Matrix
         zs = convert(Matrix{Float64}, aes.z)
 
-        if isnothing(xs)
+        if xs === nothing
             xs = collect(Float64, 1:size(zs)[1])
         end
-        if isnothing(ys)
+        if ys === nothing
             ys = collect(Float64, 1:size(zs)[2])
         end
         size(zs) != (length(xs), length(ys)) &&
@@ -1635,7 +1634,7 @@ function apply_statistic(stat::ViolinStatistic,
     grouped_color = Dict{Int, Gadfly.ColorOrNothing}(1=>nothing)
     ux = unique(aes.x)
     uxflag = length(ux) < length(aes.x)
-    colorflag = !isnothing(aes.color)
+    colorflag = aes.color !== nothing
 
     uxflag && (grouped_y = Dict(x=>aes.y[aes.x.==x] for x in ux))
 
@@ -1702,7 +1701,7 @@ function minimum_span(vars::Vector{Symbol}, aes::Gadfly.Aesthetics)
             end
         end
 
-        if isnothing(span) || (!isnothing(dataspan) && dataspan < span)
+        if span === nothing || (dataspan !== nothing && dataspan < span)
             span = dataspan
         end
     end
@@ -1715,7 +1714,7 @@ function apply_statistic(stat::JitterStatistic,
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
     span = minimum_span(stat.vars, aes)
-    isnothing(span) && return
+    span === nothing && return
 
     rng = MersenneTwister(stat.seed)
     for var in stat.vars
@@ -1756,7 +1755,7 @@ function apply_statistic(stat::BinMeanStatistic,
     Tx = eltype(aes.x)
     Ty = eltype(aes.y)
 
-    if isnothing(aes.color)
+    if aes.color === nothing
         (aes.x, aes.y) = mean_by_group(aes.x, aes.y, breaks)
     else
         groups = Dict()
@@ -1828,8 +1827,8 @@ function apply_statistic(stat::EnumerateStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    has_x = !isnothing(aes.x)
-    has_y = !isnothing(aes.y)
+    has_x = aes.x !== nothing
+    has_y = aes.y !== nothing
 
     if stat.var == :x && !has_x && has_y
         aes.x = collect(1:length(aes.y))
@@ -1870,14 +1869,14 @@ function apply_statistic(stat::VecFieldStatistic,
                          scales::Dict{Symbol, Gadfly.ScaleElement},
                          coord::Gadfly.CoordinateElement,
                          aes::Gadfly.Aesthetics)
-    xs = isnothing(aes.x) ? nothing : Float64.(aes.x)
-    ys = isnothing(aes.y) ? nothing : Float64.(aes.y)
+    xs = aes.x === nothing ? nothing : Float64.(aes.x)
+    ys = aes.y === nothing ? nothing : Float64.(aes.y)
 
     if isa(aes.z, Function)
-        if isnothing(xs) && !isnothing(aes.xmin) && !isnothing(aes.xmax)
+        if xs === nothing && aes.xmin !== nothing && aes.xmax !== nothing
             xs = range(aes.xmin[1], stop=aes.xmax[1], length=stat.samples)
         end
-        if isnothing(ys) && !isnothing(aes.ymin) && !isnothing(aes.ymax)
+        if ys === nothing && aes.ymin !== nothing && aes.ymax !== nothing
             ys = range(aes.ymin[1], stop=aes.ymax[1], length=stat.samples)
         end
 
@@ -1886,10 +1885,10 @@ function apply_statistic(stat::VecFieldStatistic,
     elseif isa(aes.z, Matrix)
         zs = Float64.(aes.z)
 
-        if isnothing(xs)
+        if xs === nothing
             xs = collect(Float64, 1:size(zs)[1])
         end
-        if isnothing(ys)
+        if ys === nothing
             ys = collect(Float64, 1:size(zs)[2])
         end
         if size(zs) != (length(xs), length(ys))
@@ -1982,8 +1981,8 @@ function apply_statistic(stat::EllipseStatistic,
     aes::Gadfly.Aesthetics)    
 
     Dat = [aes.x aes.y]
-    colorflag = !isnothing(aes.color)
-    groupflag = !isnothing(aes.group)
+    colorflag = aes.color !== nothing
+    groupflag = aes.group !== nothing
     aes_color = colorflag ? aes.color : fill(nothing, length(aes.x)) 
     aes_group = groupflag ? aes.group : fill(nothing, length(aes.x))
     CT, GT = eltype(aes_color), eltype(aes_group)
@@ -2054,7 +2053,7 @@ function apply_statistic(stat::DodgeStatistic,
                             coord::Gadfly.CoordinateElement,
                             aes::Gadfly.Aesthetics)
 
-    isnothing(aes.color) && return
+    aes.color === nothing && return
     nbars = length(unique(aes.color))
     othervar = (stat.axis == :x) ? :y : :x
     vals = getfield(aes, stat.axis)
diff --git a/src/ticks.jl b/src/ticks.jl
index 2e4c5710d..aae6954d5 100644
--- a/src/ticks.jl
+++ b/src/ticks.jl
@@ -214,7 +214,7 @@ function optimize_ticks(x_min::DateTime, x_max::DateTime; extend_ticks::Bool=fal
                     # TODO: manually setting scale with :day, :minute, etc
                 end
 
-                if isnothing(scale)
+                if scale === nothing
                     for proposed_scale in [Day(1), Hour(1), Minute(1),
                                            Second(1), Millisecond(100),
                                            Millisecond(10), Millisecond(1)]
@@ -225,7 +225,7 @@ function optimize_ticks(x_min::DateTime, x_max::DateTime; extend_ticks::Bool=fal
                     end
                 end
 
-                if isnothing(scale)
+                if scale === nothing
                     scale = Millisecond(1)
                 end
 
diff --git a/src/varset.jl b/src/varset.jl
index 9c3f31e42..ce909e502 100644
--- a/src/varset.jl
+++ b/src/varset.jl
@@ -45,7 +45,7 @@ macro varset(name::Symbol, table)
         push!(parameters, Expr(:kw, var, default))
         push!(inherit_parameters, Expr(:kw, var, :(b.$var)))
         if typ==:ColorOrNothing
-            push!(parsed_vars, :(isnothing($(var)) ? nothing : parse_colorant($(var))))
+            push!(parsed_vars, :($(var) === nothing ? nothing : parse_colorant($(var))))
         else
             push!(parsed_vars, :($(var)))
         end