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RE: Sorting Eigenvalues/EigenVe

  • To: mathgroup at
  • Subject: [mg8158] RE: [mg8099] Sorting Eigenvalues/EigenVe
  • From: Ersek_Ted%PAX1A at
  • Date: Sat, 16 Aug 1997 11:51:02 -0400
  • Sender: owner-wri-mathgroup at

Dr. Slater wrote:

|Is there an easy way to sort the results of EigenSystem so that the
|eigenvalues are in increasing order? I can pull them out of the results and
|sort them, but the association of the eigenvalues with the eigenvectors is

The code below should help.
It's a version of routine by Wouter
(see [mg6402] from Mar 97)

In[1]:=   ColumnSort[m_?MatrixQ, colm_Integer/;
                                         ( colm<=Dimensions[m][[2]] )]:=
               Sort[m, OrderedQ[{#1[[colm]] ,#2[[colm]] }]&]

In[2]:=   m=Table[Random[Integer, 25], {8}, {3}];

Out[2]=   (***  A Random Matrix of Integers    ***)

In[3]:=   ColumnSort[m, 1]//MatrixForm

Out[3]=  (******  The Matrix above after sorting the rows according
                              to the element in the first column.  ********)

     Ted Ersek

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