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Re: Inverse Matrix Function appears a bit wonky


From: Robert A. Macy
Subject: Re: Inverse Matrix Function appears a bit wonky
Date: Wed, 03 Nov 2004 21:39:44 -0800

That's it!  simply asking to return the value of rcond
allows me to catch a "bad" matrix.  

Thank you.  

           - Robert -

On Wed, 03 Nov 2004 14:08:34 -0700
 "Dmitri A. Sergatskov" <address@hidden> wrote:
> Robert A. Macy wrote:
> > I tried a simple test of the inverse function using a
> "made
> > up" matrix...
> > 
> > testmatrix =
> >  1 2 3 4
> >  2 2 3 3
> >  1 2 1 2
> >  3 2 2 1
> 
> Your matrix is no good. Set testmatrix(4,4)=-1 and try
> again :)
> 
> > What do I do to make certain octave doesn't do these
> > erroneous inverse calculations the next time I go to
> use
> > the inverse function?
> > 
> 
> Instead of b=inv(a), you can try [b,r]=inv(a), and check
> that r is not too small.
> 
> >             - Robert -
> 
> Cheers,
> 
> Dmitri.



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