scipy/scipy — pull request #388 by fabianp (2012-12-18 10:06:15+00:00)
Title: DOC: clarification on the `which` parameter of ARPACK.

I've had a hard time understanding the `which` parameter of ARPACK, so
I'm submitting this patch with the hope that it becomes clearer.

Changes:

* Eigenvectors have all norm 1, thus the parameter `which` is
applied to eigenvalues and not eigenvectors.

* Clarification on what magnitude means in the context of
complex eigenvalues.

* Clarification on what 'LA', 'SA' means. ARPACK docs refer to them
as Largest/Smallest Algebraic value: those are real numbers with
its respective sign (not in absolute value). I could not understand
what was meant before as `Largest Amplitude`.