tools/rw-heatmaps: fix HeatMapGrid documentation

Signed-off-by: Ivan Valdes <[email protected]>

tools/rw-heatmaps/pkg/chart/heatmap_grid.go

@@ -20,13 +20,13 @@ type HeatMapGrid struct {
 	z    [][]float64 // The Z values should be arranged in a 2D slice.
 }
 
-// Len returns the number of elements in the grid.
+// Dims returns the number of elements in the grid.
 // It implements the plotter.GridXYZ interface.
 func (h *HeatMapGrid) Dims() (int, int) {
 	return len(h.x), len(h.y)
 }
 
-// ValueAt returns the value of a grid cell at (c, r).
+// Z returns the value of a grid cell at (c, r).
 // It implements the plotter.GridXYZ interface.
 func (h *HeatMapGrid) Z(c, r int) float64 {
 	return h.z[r][c]