Nested for loop, too slow

Hello, I have a 2464 x 2464 matrix (44 block matrixes 56x56). I need an algorithm to put at 0 at each iteration the rows and columns i, i + 56, i + 112, i + 168 .... i + 2352.

I wrote this:

for j=1:56
    D=A;
for i=1:43
    D(j,1:end)=0;
    D(1:end,j)=0;
    for m=j+(i*56)
D(m,1:end)=0;
D(1:end,m)=0;
    end
C=D;
xlswrite('results.xlsx',C,j);
end
end

and, apparently, it works, but it's so slow. Too slow! Any suggestion?

Answer 1

[Bob Thompson]

It looks like you want to blank the entire row, correct?

A = 1:56:2464;
D(A,:) = 0;

EDIT** Change variable names as you need to, I just used generic ones without looking at what exactly you used.

[Raffaele Giammetti]

Yes, so simple so perfect. Shame on me!

Thank you very much :)