I am interested how to create a diagonal matrix from an array of matrices. I created an array of matrices in MATLAB:
X<62x62x1000> it consists of 1000 matrices with dimensions 62x62
I want to create a matrix of dimensions 62000x62000 with 1000 sub matrices from array X along main diagonal.
Do you have any clue how to do this, except M=blkdiag(X(:,:,1), X(:,:,2), X(:,:,3)...) because that would be to much writing.
A possible solution
M = kron(speye(1000),ones(62)); M(logical(M)) = X(:); With kron a 62000*62000 sparse matrix M is created that contains 1000 blocks of ones on its diagonal, then replace ones with elements of X.
You can flatten out your input matrix into a column vector using (:) indexing and then pass it to diag to place these elements along the diagonal of a new matrix.
result = diag(X(:)) This will order the elements along the diagonal in column-major order (the default for MATLAB). If you want a different ordering, you can use permute to re-order the dimensions prior to flattening.
It's important to note that your resulting matrix is going to be quite large. You could use spdiags instead to create a sparse diagonal matrix
spdiags(X(:), 0, numel(X), numel(X)) A very controversial eval call can solve this very lazily, although I suspect there is a much better way to do this:
evalstring = ['M=blkdiag(']; for i = 1:999 evalstring = [evalstring, 'X(:,:,', num2str(i),'),']; end evalstring = [evalstring, 'X(:,:,1000));']; eval(evalstring); 