Re: Eigenvector routine....

Hi Rob,
even for a 3x3 matrix, finding the lowest eigenvalue is not entirely
trivial. It amounts to finding the zeros of the characteristic equation
which is obviously cubic. Google for Vieta equation (mathworld.com has
a nice explanation)

Good luck,

Jan

Rob McDonald wrote:
> Does anyone know of a small, simple, freely available Eigenvector routine?
>
> My application has been developed using jacobi.c (and eigsrt.c) from
> Numerical Recipes. This works well for me, but the application will soon be
> released under the GPL, and the nice folks at NR don't want their source
> distributed around. I could just leave stubs in place and require people to
> get the routines themselves, but I'd rather replace the routines with
> something more available.
>
> I don't really want to introduce a dependency on a large numerical toolkit,
> instead, I'd like to just pull in the relevant code. Something small and
> simple is preferred over the latest & greatest.
>
> In fact, the problem is nearly trivial. Find the eigenvectors & eigenvalues
> of a real, symmetric, 3x3 matrix. Then, all I need is the eigenvector with
> the smallest eigenvalue.
>
> With such a small problem, I'm surprised there isn't an even simpler
> approach...
>
> Any help will be appreciated,
>
> Rob

.