I believe the problem is that syminv(A) requires that A be
positive definite to generate a normal inverse. Your A is
not positive definite, so syminv(A) returns a g2 inverse.
> -----Original Message-----
> From: Jiang, Tao [mailto:[email protected]]
> Sent: Friday, September 06, 2002 3:57 PM
> To: '[email protected]'
> Subject: st: Matrix calculation
>
>
> I was doing some matrices calculation, but got some problem.
> What I had is
> a simple matrix:
>
> A = (1,2\2,1)
>
> and if I do B = inv(A), I got the correct matrix; if I do B =
> syminv(A),
> I got the following:
>
> . mat A = (1,2\2,1)
> . mat list A
>
> symmetric A[2,2]
> c1 c2
> r1 1
> r2 2 1
> . mat iA=syminv(A)
>
> . mat list iA
>
> symmetric iA[2,2]
> r1 r2
> c1 1
> c2 0 0
>
> Is there some reason why?
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
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