Re: Forcing real eigenvalues with 'eigs'?

[Jaroslav Hajek]

On Thu, Jan 22, 2009 at 1:39 PM, Søren Hauberg <address@hidden> wrote:
> tor, 22 01 2009 kl. 13:35 +0100, skrev Francesco Potortì:
>> >Is it possible to force 'eigs' to produce real eigenvalues? I'm
>> >computing eigenvalues of a real symmetric matrix, but I'm still getting
>> >complex eigenvalues (numerical issues I guess), so it would be nice if I
>> >could force them into being real.
>>
>> Have you looked at the numbers?  If the imaginary part is very small
>> compared to the real one, you can just discard it using real().  If not,
>> you may have stability problems.
>
> Yeah, I can just discard them using real (they are indeed quite small).
> It just seems to me that it would be better if I could constraint 'eigs'
> to working only with real values.
>

I think this is a bug - eigs should discover a symmetric case.


-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz