How can I extract the main diagonal of a sparse matrix?

Question

How can I extract the main diagonal of a sparse matrix? The matrix is created in scipy.sparse. I want equivalent of np.diagonal(), but for sparse matrix.

Answer 1

A sparse matrix has a diagonal method:

M.diagonal()

http://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.csc_matrix.diagonal.html

The numpy diagonal is a little more powerful, allowing you to specify an off diagonal

M.A.diagonal(2)