# [Maxima] Can't find eigenvalues

Javed Alam jalam1001 at gmail.com
Wed Dec 10 23:50:37 CST 2008

```You can try the following function of Maxima since your matrix is all
numeric

m : matrix([14,32,50],[32,77,122],[50,122,194]);

e : eigens_by_jacobi(m);

More details at
http://www.eng.ysu.edu/~jalam/engr6924s07/sessions/session15/session15.htm

Javed

http://www.eng.ysu.edu/~jalam/engr6924s07/<http://www.eng.ysu.edu/~jalam/engr6924s07/sessions/session15/session15.htm>

On Wed, Dec 10, 2008 at 11:52 PM, Noparit Jinuntuya <fscinpr at yahoo.com>wrote:

> Many thanks.
>
> For this bug, it may be interesting to note that, by little modification
>
> (%i1) b:matrix([0,-1/4,0,0],[1/4,0,0,0],[0,0,0,-1/4],[0,0,1/4,0])\$
> (%i2) eigenvalues(4*b);
>
> Maxima give the correct answer,
>
> (%o2) [[-%i,%i],[2,2]]
>
> Noparit
>
> --- On *Wed, 12/10/08, Barton Willis <willisb at unk.edu>* wrote:
>
> From: Barton Willis <willisb at unk.edu>
> Subject: Re: [Maxima] Can't find eigenvalues
> To: fscinpr at yahoo.com
> Cc: maxima at math.utexas.edu
> Date: Wednesday, December 10, 2008, 3:25 AM
>
>
> You found a bug, I'm sorry to say. I'm pretty sure that the bug is due
> to a faulty computation of the multiplicities of the roots of the
> characteristic polynomial:
>
>  (%i26)
>  solve(g33664^2*(g33664^2+1/16)+(g33664^2+1/16)/16,g33664);
>  (%o26) [g33664=-%i/4,g33664=%i/4]
>
>  (%i27) multiplicities;
>  (%o27) [1,1]
>
> I think (%o27) should be [2,2]. I can't think of a workaround; I'll
> file a bug report.
>
> Barton
>
> -----maxima-bounces at math.utexas.edu wrote:
>  -----
>
>
> >I'm trying to find the eigenvalues of a simple matrix
> >
> >b:matrix([0,-1/4,0,0],[1/4,0,0,0],[0,0,0,-1/4],[0,0,1/4,0]);
> >
> >by
> >
> >eigenvalues(b);
> >
> >But Maxima give me
> >
> >part fell off end.
> >#0:
> >eigenvalues(mat=matrix([0,-1/4,0,0],[1/4,0,0,0],[0,0,0,-1/4],[0,0,1/4,0]))
> >(eigen.mac line 94)
> >-- an error.  To debug this try debugmode(true);
> >
> >What wrong with this? Can anyone help?
> >
> >Noparit Jinuntuya
> >Department of Physics, Kasetsart University
> >Thailand.
> >
> >
> >
> >
> >
> >_______________________________________________
> >Maxima mailing list
> >Maxima at math.utexas.edu
> >http://www.math.utexas.edu/mailman/listinfo/maxima
>
>
>
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>
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