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From Sean Owen <>
Subject Re: Detecting rank-deficiency, or worse, via QR decomposition
Date Thu, 04 Apr 2013 14:26:16 GMT
I think that's what I'm saying, yes. Small rows X shouldn't become
large rows of A -- and similarly small changes in X shouldn't mean
large changes in A. Not quite the same thing but both are relevant. I
see that this is just the ratio of largest and smallest singular
values. Is there established procedure for evaluating the
ill-conditioned-ness of matrices -- like a principled choice of
threshold above which you say it's ill-conditioned, based on k, etc.?

On Thu, Apr 4, 2013 at 3:19 PM, Koobas <> wrote:
> So, the problem is that the kxk matrix is ill-conditioned, or is there more
> to it?

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