www.pudn.com > NSGAII.rar > crowding_distance.m, change:2009-07-16,size:2674b


function f = crowding_distance(x,problem) 
% This function calculates the crowding distance

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%  Copyright (c) 2009, Aravind Seshadri
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[N,M] = size(x); 
switch problem 
    case 1 
        M = 2; 
        V = 6; 
    case 2 
        M = 3; 
        V = 12; 
end 
 
% Crowding distance for each front 
for i = 1 : length(F(front).f) 
    y(i,:) = x(F(front).f(i),:); 
end 
for i = 1 : M 
    [sorted(i).individual,sorted(i).index] = sort(y(:,V + i)); 
    distance(sorted(i).index(1)).individual = Inf; 
    distance(sorted(i).index(length(sorted(i).index))).individual = Inf; 
end 
 
[num,len] = size(y); 
% Initialize all the distance of individuals as zero. 
for i = 1 : M 
    for j = 2 : num - 1 
        distance(j).individual = 0; 
    end 
    objective(i).range = ... 
                sorted(i).individual(length(sorted(i).individual)) - ... 
                sorted(i).individual(1); 
        % Maximum and minimum objectives value for the ith objective 
end  
% Caluclate the crowding distance for front one. 
for i = 1 : M 
    for j = 2 : num - 1 
        distance(j).individual = distance(j).individual + ... 
            (sorted(i).individual(j + 1) - sorted(i).individual(j - 1))/... 
            objective(i).range; 
        y(sorted(i).index(j),M + V + 2) = distance(j).individual; 
    end 
end