Path: news.mathworks.com!not-for-mail
From: <HIDDEN>
Newsgroups: comp.soft-sys.matlab
Subject: Re: unsorted eigenvalues
Date: Wed, 4 Feb 2009 11:11:01 +0000 (UTC)
Organization: Universit&#233; Paris-Est
Lines: 19
Message-ID: <gmbt45$hh1$1@fred.mathworks.com>
References: <fdhvq6$hok$1@fred.mathworks.com> <muytzpeaonp.fsf@G99-Boettcher.llan.ll.mit.edu>
Reply-To: <HIDDEN>
NNTP-Posting-Host: webapp-02-blr.mathworks.com
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
X-Trace: fred.mathworks.com 1233745861 17953 172.30.248.37 (4 Feb 2009 11:11:01 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Wed, 4 Feb 2009 11:11:01 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 1699797
Xref: news.mathworks.com comp.soft-sys.matlab:515937


Peter Boettcher <boettcher@ll.mit.edu> wrote in message <muytzpeaonp.fsf@G99-Boettcher.llan.ll.mit.edu>...
> "Robert Sparr" <robertdotsparr@NOSPAMsri.com> writes:
> 
> > I am aware that the eigenvectors have been sorted so that
> > eigenvector index i corresponds to eigenvalue index i, and I
> > know how to reconstruct the signal with the sorted output
> > given by eig(), but that is not sufficient.  I also need to
> > know the indexes that the significant eigenvalues had before
> > they were sorted.
> 
> What is the true order of the roots of this polynomial?
> 
> x^3 - 2*x^2 +3*x -3
> 
> -Peter

 I have the same problem and speaking about the order of the eigenvalues it is important because the eigenvectors correspond, in my case, to a rotation matrix used to obtain principal coordinates which changes with frequency. so if eig() organizes the eigenvectors i will never know which vector is which from one frequency to the other as the maximum eigenvalue is not always on the same direction.

Morad