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Re: QUESTION (EigenVectors)

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  • Subject: [mg19410] Re: QUESTION (EigenVectors)
  • From: rfinley at (Richard Finley)
  • Date: Mon, 23 Aug 1999 13:57:20 -0400
  • Organization: Internet Doorway, Inc. --
  • References: <7pl79i$>
  • Sender: owner-wri-mathgroup at

Since this is a Mathematica newsgroup, I presume you mean using Mathematica in which
case it is easy...if M is your matrix then
Eigensystem[M] will give you the eigenvalues and eigenvectors.  If you are
just looking for an algorithm for writing code yourself, try Numerical
Recipes by Press et al.  or even better, use one of the libraries like IMSL
or NAG to save yourself a lot of time and aggravation.  regards, RF

Christian Langis wrote in message <7pl79i$ch0 at>...
>Hi there.
>I am a a computer science student; and that is probably why
>this question may seem deprived of any chalenge to you. But it
>is quite challenging to me.
>The question is: how do you extract the 1st EigenVector from a
>3x3 matrix (and optionally 2nd and 3rd)?
>I read a solution which forces the person to extract the 3
>roots of a 3rd degree polynomial. And this has to be done by
>hand of course.
>Hence, it is possible to compute that manually. But I am rather
>looking for an algorithm do carry this task, a solution which
>does not involve any manual evaluation (such as root extraction).
>Therefore do you know any algorithm/source code to do that (or
>know where to find it)?

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