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Re: LU factorization in Mathematica

  • To: mathgroup at
  • Subject: [mg20680] Re: LU factorization in Mathematica
  • From: alanw at
  • Date: Sun, 7 Nov 1999 02:10:12 -0500
  • References: <7vrcnc$>
  • Sender: owner-wri-mathgroup at

    This was a mystery to me too the first time I tried it. Here's the
solution. I don't remember where to find this in the docs or in the

First, the LU factorization:

    {lu, p, cn} = LUDecomposition[t]

Then you do this:

    Map[MatrixForm, {l, u} = LUMatrices[lu]]

Good luck,

In article <7vrcnc$2ob at>,
  "Peltio" <peltio at> wrote:
> I apologise for this question but I did not find what iI was looking
> on the Big Book.
> Any hint will be appreciated.
> LUDecomposition returns a matrix that is a combination of the L and U
> matrices. But what kind of combination?
> How can I recover the two matrices L and U?
> What is the meaning of the pivoting vector (Does P[[k]]=j means that
> k has been swapped with row j ?)
> And what are the meaning of the elements returned by LUfactor (in the
> GaussianElimination package ), which returns a different pivot vector
> (and matrix as well)?
> Thanks in advance,
> Peltio
> peltio AT iname DOT com
> warning: Antispam return address <ON>

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