       Sorting eigenvectors by eigenvalue

• To: mathgroup at christensen.cybernetics.net
• Subject: [mg2054] Sorting eigenvectors by eigenvalue
• From: valentin at wam.umd.edu (William F. Campbell)
• Date: Mon, 18 Sep 1995 01:50:46 -0400
• Organization: University of Maryland, College Park

```  I'm trying to use Sort to sort eigenvectors by eigenvalue.  The eignevectors
are in a list of lists called vecs, and the eigenvalues in vals after the
following function call on matrix aa:

{vals,vecs}=Eigensystem[aa]

Then I want to define an ordering function p so I can use Sort[vecs,p].
I tried the following:

p[vecs[[i_]],vecs[[j_]]]:=Greater[Abs[vals[[i]],Abs[vals[[j]]]]

Mathematica wont parse vecs[[i_]] saying that i is neither an integer nor
a list of integers.  How can I accomplish what I want to do?
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|  Bill Campbell                                                             |
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```

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