Symmetric matrices and eigs

It would we good if you could use the sigma value “sr” in function eigs for symmetric matrices, too.

Does sigma = "sa" work for you?

sigma = "sa";
eigs (A, k, sigma)

Octave’s eigs function might need some update GNU Octave - Bugs: bug #52999, Syntax change in eigs [Savannah] and the documentation looks confusing to me. Matlab sees both options as equal. Maybe there was a distinction for historical reasons.

Furthermore looking at the implementation and following sigma through the m-code, "sa" and "sr" are identical. Any error messages are “artificial” :sweat:

There could be some distinction between "sa" and "sr" within the __eigs__.cc internal function, but the easiest check was if replacing the one by the other works for you :wink:

“sa” seems to work. Thanks for your help.