[SciPy-User] Help required regding Eigenvectors

Andrew Dessler adessler@tamu....
Tue Sep 21 12:28:27 CDT 2010

Sudheer Phani <bpsu <at> james.hut.fi> writes:

> Hello All,
>    I have been encountering some strange problems with the calculation of
> eigen vectors using python. The problem is with the sign of the eigen
> vectors calculated. On Very few occasions the eigen vectors calculated
> using python have an opposite sign than the actual eigenvectors, though
> the magnitude is correct.
> Can any one of you plz help me in this regard and suggest me some solution
> if you have encoutered similar problems .
> Any help in this regd is appreciated
> Thanks in Advace
> regds
> Sudheer

I had a similar experience.  However, I solved it when I realized that the eig
routine in scipy.linalg does not necessarily return the biggest
eigenvalue/eigenvector first.  It often does, but not always.  Once I realized I
had to find the biggest one on my own, the problem was solved.

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