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From: "Bruno Luong" <b.luong@fogale.findmycountry>
Newsgroups: comp.soft-sys.matlab
Subject: Re: RQ decomposition
Date: Sun, 5 Oct 2008 02:23:02 +0000 (UTC)
Organization: FOGALE nanotech
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"David Doria" <daviddoria@gmail.com> wrote in message <gc8uop$2nh$1@fred.mathworks.com>...
> Bruno,
> 
> Could you explain in a couple of sentences what that is doing in a little bit "mathy" terms? ie. I've never seen a "flip upside down" step in a linear algebra kind of definition- can you explain why that is done?
> 

Hi,

Flipping upside down is multiplying a permutation matrix on the left side. Flipping rows (also in the above but only m rows, not n), is multiplying a permutation matrix on the right side.

I use permutation matrices for the purpose to transform a lower triangular matrix to upper one.

Bruno