Crowding Distance

[ayushmankd]

There is an error in Crowding Distance function.
It should be values1[i-1] - values1[i+i]
and values2[i-1] - values2[i+1]

[Arexh]

I agree.

[XuhuaYY]

I think it's not just this error
sorted1 = sort_by_values(front, values1[:])
sorted2 = sort_by_values(front, values2[:])
the obtained two ordinal lists must be opposite, because front is a non-dominated solution, then their distance calculations have been misplaced, and should be changed to:

---

def crowding_distance(values1, values2, front):
    distance = [0 for i in range(0,len(front))]
    sorted1 = sort_by_values(front, values1[:])
    # sorted2 = sort_by_values(front, values2[:])
    distance[0] = 4444444444444444
    distance[len(front) - 1] = 4444444444444444
    for k in range(1,len(front)-1):
        distance[k] = abs(values1[sorted1[k+1]] - values1[sorted1[k-1]])/(max(values1)-min(values1))
        distance[k] = distance[k]+ abs(values2[sorted1[k+1]] - values2[sorted1[k-1]])/(max(values2)-min(values2))
    return distance