no repetition in the result of a roulette wheel selection function

Please, I would like to ask someone a little question: what should I do if I have to write a roulette selection function for a genetic algorithm in which the resulting numbers have no repetition. In example, if I write the selectionroulette of matlab toolbox:

 function parents = selection3roulette(expectation,nParents,options)
 % example
 nParents=14;    
 expectation=[1.6098;
    0.9294;
    1.1383;
    1.9716;
    1.3941;
    1.2470;
    0.9858;
    0.8817;
    1.0539;
    2.7883];

 expectation = expectation(:,1);
 wheel = cumsum(expectation) / nParents;

 parents = zeros(1,nParents);

 for i = 1:nParents
    r = rand;
    for j = 1:length(wheel)
        if(r < wheel(j))
            parents(i) = j;
            break;
        end
    end
 end
 disp('parents=');disp(parents);

at the end I could obtain : parents= [5 5 1 5 7 6 2 7 5 8 1 5 3 8] instead I wolud have different elements into the array... Thank you very much....

Answer 1

[Sean de Wolski]

doc randperm

maybe?

[Cristina]

thank you very much, Sean

I'm trying with this command..but I think I'm doing something wrong...

nParents=14;

expectation=[1.6098;

0.9294;

1.1383;

1.9716;

1.3941;

1.2470;

0.9858;

0.8817;

1.0539;

2.7883];

expectation = expectation(:,1);

wheel = cumsum(expectation) / nParents;

parents = zeros(1,nParents);

for i = 1:nParents

% r = rand;

nran = randperm(nParents)

r=nran/nParents

for j = 1:length(wheel)

if(r < wheel(j))

parents(i) = j

break;

end

end

end

Anyway, thank you a lot!!!

[Sean de Wolski]

perhaps r(i) in the while criterion?

r<wheel(i) means ALL r < wheel(i) is that what you want? or do you want a specific r?

(Sorry, no roulette expert - blackjack is where the fun is!)

[Cristina]

thank you for your useful (and funny!!)answer..

Now I'm going to try with the while cycle...

Otherwise I'll turn to blackjack too :)