why doesnt it works

for i = 1 :1: N
    for j = 1 :1: N
        if u(i,j) < 1-a(i,j) && N<1- (u(i,j)/(1-a(i,j)))
            z= (1-a(i,j))*N
        end
    end
end

[Rik]

This time I edited your question for you. Next time, please use the tools explained on this page to make your question more readable.

What do you mean by 'it doesn't work'?

[Peter Perkins]

Also, you don't need loops at all.

z = zeros(size(a));
i = (u < 1-a) && (N < 1 - u./(1-a))
z(i) = (1-a(i)) .* N;

[Nirajan Khatri]

@ Rik thank you, i have u matrix and a matrix so i was trying to use conditional loop, next time i will surely do it

[Nirajan Khatri]

@ Peter Perkins Sir thank you