How can I assign a value to the diagonals of a 4-D matrix using linear indexing in MATLAB?

Question

I have a 4-D matrix A of size NxNxPxQ. How can I easily change the diagonal values to 1 for each NxN 2-D submatrix in a vectorized way

Answer 1

Incorporating gnovice's suggestion, an easy way to index the elements is:

[N,~,P,Q]=size(A);%# get dimensions of your matrix

diagIndex=repmat(logical(eye(N)),[1 1 P Q]);%# get logical indices of the diagonals    
A(diagIndex)=1;%# now index your matrix and set the diagonals to 1.