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MathGroup Archive 2004

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Matrix Inversion

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48022] Matrix Inversion
  • From: Gregor <athlonicNOSPAM at yahoo.com>
  • Date: Fri, 7 May 2004 04:29:40 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I try to invert a badly conditioned 8x8 matrix trough the normal 
Inverse[M] command

I receive the bad conditioning warning message, telling me that 
significant numerical errors could be made. Indeed this is the case as 
M.M^-1 is not an Identity matrix at all.

When I use PseudoInverse[M] I don't get the warning (that's normal), but 
I don't get a correctly inverted matrix. M.M^-1 is also not identity at all.

I did chop the resulst of M.M^-1 but I have very big numbers outside of 
the diagonal in the first case and numbers of the order of 10^-2 in the 
PseudoInverse case.

The matrix is correctly inverted in another system, but I would like to do 
everything in Mathematica as my whole program is in Mathematica.

What should I do?


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