Re: eigs fails for scalars and 2x2 matrices

[John W. Eaton]

On 06/26/2013 03:59 PM, Jordi Gutiérrez Hermoso wrote:
> On 26 June 2013 04:28, John W. Eaton<address@hidden>  wrote:
> > eigs fails for scalars and 2x2 matrices, apparently intentionally
> > given the error message.  Is this a limitation of ARPACK?  Should we
> > work around this problem by calling eig for these cases?
>
> This was Bateman's response:
>
>      
> https://mailman.cae.wisc.edu/pipermail/octave-maintainers/2011-July/024272.html

Hmm.  Well Matlab apparently handles eigs (rand (N)) for N = 2, 3, 4, 5 
6, 7, 8, ...

Octave's eigs doesn't start working until N >= 9, even though it is 
supposed to be calculating the 6 largest eigenvalues by default.  I 
guess Matlab takes that to be all the eigenvalues if the dimension is 
less than 6.

jwe