MATLAB: How to avoid for nested loops with if condition

2d arrayfor loopif statement

Hello,
I have big matrixes of same size, and am suing for loop with if statement, which is bottleneck in my code and is very slow. How would it be possible to optimize it?
    for i=1:n1
    for j=1:n2
    if id(i,j)==1
    if RR(i,j)==1
        id(i,x(i,j))=0;
    end
    end
    end
end
 Maybe it is possible to vectorize or use bsxfun?

Best Answer

You certainly don't need the j loop:
for row = 1:size(id)
   id(row, x(id(row, :) == 1 & RR(row, :) == 1)) = 0;
end
You could get rid of the i loop as well at the expense of memory (another array the same size as id)
mask = id == 1 & RR == 1;  %and if id and RR are logical, simply: mask = id & RR;
rows = repmat((1:size(id, 1)', 1, size(id, 2));
id(sub2ind(size(id), rows(mask), x(mask))) = 0;
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