Repeating Matrix values along a diagonal

So lets say you have a matrix A=zeros(9,9). I have the main diagonal (and other diagonals) with values of 1 going throughout the matrix. How could i get the diagonals to skip every say 3 values. So that A(1,1), A(2,2) are 1 but A(3,3) is 0 A(4,4), A(5,5) are 1 A(6,6) is 0. The main issue is i have to do this for a 400x400 matrix or i would just hardcode these values as such but that would take too long. All of this is being done in matlab.

Answer 1

[Walter Roberson]

N = 400;
temp = ones(1,N); temp(3:3:end) = 0;
A(1:N+1:end) = temp;

In the case where N is exactly divisible by the length of the pattern, use repmat(), such as

pat = [1 1 0];
repmat(pat, 1, N/length(pat))    %would work for N = 399 or 402 but not N = 400