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Re: Eigenvalues, any suggestions?

  • To: mathgroup at
  • Subject: [mg43624] Re: Eigenvalues, any suggestions?
  • From: "Eckhard Hennig" <aidev at>
  • Date: Fri, 26 Sep 2003 04:45:37 -0400 (EDT)
  • Organization: 1&1 Internet AG
  • References: <bkp2hl$d2r$>
  • Sender: owner-wri-mathgroup at

"AC" <ancow65 at> schrieb im Newsbeitrag
news:bkp2hl$d2r$1 at
> 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:


Best regards,


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

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