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Re: Inverse Matrix Function appears a bit wonky
From: |
Henry F. Mollet |
Subject: |
Re: Inverse Matrix Function appears a bit wonky |
Date: |
Fri, 05 Nov 2004 10:03:16 -0800 |
User-agent: |
Microsoft-Entourage/10.1.1.2418 |
Michael probably can give us the solution for a 4x4 with numbers between
1-10. I run the following 10 times and always got rank = 4.
octave:3> ceil(10*rand(4))
ans =
4 1 5 5
1 2 1 1
3 9 10 6
7 5 6 9
octave:4> rank(ans)
ans = 4
Henry
on 11/5/04 1:31 AM, Michael Creel at address@hidden wrote:
> For 2x2 matrices made up of integers between -3 and +3, the answer is
> obviously 14.4%. If you can't see that at first sight, try running the
> attached script. Sheesh!
> Michael
>
> On Thursday 04 November 2004 16:33, Przemek Klosowski wrote:
>> Your arbitrary test matrix is ill-conditioned so any attempt to invert
>> ...
>> accuracy. For another example, try hilb(n) * inv(hilb(n)) for n = 1,
>> 2, ..., 15. The Hilbert matrix is famously illconditioned for large n.
>>
>> it is so frequent that it's even funny: people come up with a random
>> small-dimension matrix, typically made up of smallish integers, and
>> get a singular one. Does anyone know how dense is the set of singular
>> matrices in the set of all small-size, small-value matrices? is it
>> really that dense, or are we having bad luck :)?
>>
>> p
>>
>>
>>
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Octave is freely available under the terms of the GNU GPL.
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- Inverse Matrix Function appears a bit wonky, Robert A. Macy, 2004/11/03
- Re: Inverse Matrix Function appears a bit wonky, Dmitri A. Sergatskov, 2004/11/03
- Re: Inverse Matrix Function appears a bit wonky, Robert A. Macy, 2004/11/04
- Re: Inverse Matrix Function appears a bit wonky, David Bateman, 2004/11/04
- Re: Inverse Matrix Function appears a bit wonky, John W. Eaton, 2004/11/04
- Re: Inverse Matrix Function appears a bit wonky, David Bateman, 2004/11/05
- Re: Inverse Matrix Function appears a bit wonky, John W. Eaton, 2004/11/05
- Re: Inverse Matrix Function appears a bit wonky, David Bateman, 2004/11/05
Re: Inverse Matrix Function appears a bit wonky, Geraint Paul Bevan, 2004/11/03