Re: Eigenvalues, any suggestions?

• To: mathgroup at smc.vnet.net
• Subject: [mg43624] Re: Eigenvalues, any suggestions?
• From: "Eckhard Hennig" <aidev at n-o-s-p-a-m.kaninkolo.de>
• Date: Fri, 26 Sep 2003 04:45:37 -0400 (EDT)
• Organization: 1&1 Internet AG
• References: <bkp2hl$d2r$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

"AC" <ancow65 at yahoo.com> schrieb im Newsbeitrag
news:bkp2hl$d2r$1 at smc.vnet.net...
> In[1]:=
>  data={XX\[Rule]100.,YY\[Rule]100.,ZZ\[Rule]100.,
>         XY\[Rule]0.,XZ\[Rule]0.,YZ\[Rule]0.};
>
> In[2]:=
> Eigenvalues[{{XX,XY,XZ},{XY,YY,YZ},{XZ,YZ,ZZ}}]/.data
>
> \!$$Power::"infy" \(\(:$$$$\$$\) "
>     Infinite expression \!$$1\/0.\^\(1/3$$\) encountered."\)

Just move the closing bracket a few positions to the right to evaluate the
matrix numerically *before* calculating the eigenvalues:

Eigenvalues[{{XX,XY,XZ},{XY,YY,YZ},{XZ,YZ,ZZ}} /.data]

Note that in your formulation, the eigenvalues were first computed
symbolically, and the solutions involve cubic root expressions (hence the
0^1/3 errors). Hint: check the output of this command:

Eigenvalues[{{XX,XY,XZ},{XY,YY,YZ},{XZ,YZ,ZZ}}]

Best regards,

Eckhard

--
Dr.-Ing. Eckhard Hennig
www.kaninkolo.de/ai
aidev \at kaninkolo \dot de

`

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