I have an N by M matrix and I want to store its columns in block diagonal form. This matrix is enormous, so if I can directly store it as a sparse matrix that would be helpful.
To give more detail:
X = ones(30, 1000);
And I want this without having to type it out (because the matrix actually has 1 million columns).
sparse(blkdiag(X(:,1), X(:,2), X(:,3), .... , X(:,1000)).
By the way, my best attempt is this:
a = cell(M,1);for i = 1:M [a{i}]= deal(sparse(X(:,i)));endX=blkdiag(a{:});
But I'm using a loop and am worried this is inefficient.
Best Answer