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Topic: Condition number of matrices
Replies: 5   Last Post: Jul 5, 2006 3:36 PM

 Messages: [ Previous | Next ]
 Han de Bruijn Posts: 5,094 Registered: 12/13/04
Re: Condition number of matrices
Posted: Jul 3, 2006 3:25 AM

Fijoy George wrote:

> So how does one calculate the condition number of a matrix? Given that real
> world systems are large, can we precisely calculate K(A)? Or, can we only
> hope to obtain a upper bound for K(A)?

Condition numbers are nice for theoretical considerations, but I haven't
seen they have quite a sensible meaning in practical situations. You can
calculate them _after_ you have already done a lot of work (i.e. solving
the equations) while it is suggested that you should rather know about
Condition Numbers _before_ doing so.

With Least Squares problems, though, theory leads to the insight that it
is wise to use normed equations, that is: weighted with the trace of the
element matrices OR length of the vector of equation coefficients, which
is the same thing. This doesn't help in actually predicting how large or
how small the C.N. will be, in the end.

Han de Bruijn

Date Subject Author
7/2/06 Fijoy George
7/2/06 Toni Lassila
7/5/06 Doug Schwarz