How to convert matrix to a stack of diagonal matrices based on every row?

Question

I have a matrix:

A = [1 1 1
     2 2 2
     3 3 3]

Is there a vectorized way of obtaining:

B = [1 0 0 
     0 1 0
     0 0          


        

Answer 1

An alternative, which (for me) is faster than any of the methods benchmarked above (for large and small matrices) is

[m,n] = size(A);
Z(n,m*n) = 0;
for idx = 1:n
     Z(idx,((idx-1)*m+1):(idx*m)) = A(:,idx);
end
Z = reshape(Z,m*n,n);