How do I get data from each step in a loop?

Hello.

I want my array resu to save all date for each n=1,2,3... in row n, and start the same procedure for next n. So in the first row in resu i want to have an array when n=1 while looping m and j. Second row scould be an array when n=2 while looping m and j. And so on, all the way until n=N.

Any suggestions what iam doing wrong?

My code:

resu = zeros([N,length(t)]);
u=zeros(size(t));

for n=1:N
    for m=1:N
        for j=1:Q 
            Omega=omegaakse(j);
            u=u+abs(Gu(n,m,j))*sqrt(2*domega)*cos(Omega.*t+2*pi*rand);
        end 
     end
    resu(n,:) = u;
end

where t i a time vector.