[SciPy-user] Bug in inverse matrixcalculation for "scipy_core-0.8.4.win32-py2.3.exe"
Randewijk P-J <pjrandew@sun.ac.za>
pjrandew at sun.ac.za
Wed Dec 14 10:13:07 EST 2005
Now that you metion it... "sometimes" the inverse of some of my
supposedly singular matrixes has "very large" values, because the
determinant is actually not zero, but a "very small" value... e.g.
>>> linalg.det(m)
-1.5717747464951435e-006
>>>
> -----Original Message-----
> From: scipy-user-bounces at scipy.net
> [mailto:scipy-user-bounces at scipy.net] On Behalf Of Nils Wagner
> Sent: 14 December 2005 17:01
> To: SciPy Users List
> Subject: Re: [SciPy-user] Bug in inverse matrixcalculation
> for "scipy_core-0.8.4.win32-py2.3.exe"
>
>
> Frank wrote:
> >"On this note. Is there a way of determining before hand in
> scipy if a
> >matrix is singular, say by calculating its rank, e.g.:"
> >
> >if det(matrix) = 0, then the matrix is singular
> >
> >_______________________________________________
> >SciPy-user mailing list
> >SciPy-user at scipy.net http://www.scipy.net/mailman/listinfo/scipy-user
> >
> This is not very reliable when using floating point
> operations. See the book by Carl D. Meyer "Matrix analysis
> and applied linear algebra" SIAM 2000 especially chapter 6 p.
> 466 Example 6.1.2
>
> Nils
>
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