MATLAB: Getting ‘output argument’ error when calling function

Question

I have written this below function :

function [winner_index] = Auction(match_fit,match_index,cbid)
bidmax = 0;
m = match_fit;
w = match_index;
for i = 1:length(m)
    bid(i) = cbid*m(i,:);
    effectiveBid (i)= bid(i)+randn;
    if effectiveBid(i) > bidmax
        winner_index = w(i);
        bidmax = effectiveBid(i);
    end
end
end

Previously when I run this some times it is ok, sometime it was giving the below error " Output argument "winner_index" (and maybe others) not assigned during call to "Auction".

and now I am calling this function inside a loop. It is continuously showing the same error. I don't know why 🙁

[SL: edited to apply code formatting. Brinta, in the future please use the {}Code button to format your code.]

Answer 1

If effectiveBid(i) > bidmax is not true during any of the iterations, the variable winner_index will never be assigned a value. When the function returns, it tries to take the value of winner_index in the function and return it as the output. But winner_index doesn't exist so MATLAB throws an error.

Define winner_index to a default value before the for loop.