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Re: problem inverting matrix [message #33424]

Mon, 06 January 2003 12:10

Ralf Flicker
Messages: 19
Registered: October 2001

Junior Member

Lars Schmidt wrote:
>
> Hello,
>
> I desperately hope someone of you has got an idea.
> I try to invert a matrix using "invert" of course with floating-point
> values.
> I get like explosion of values although the status variable I used with
> "invert" did not return any error and I also used the "/double" keyword.
> Has anybody an idea or experience with that. Are these numerical problems of
> the gaussian ellemination??
> Tanks in advance.
>
> LARS SCHMIDT.

Maybe try a double precision singular value decomposition to see
if something funny is up with your matrix:

svdc,Your_Matrix,sv,u,v,/double
plot_io,sv(reverse(sort(sv)))/max(sv),psym=-1

If it looks ok, I don't know why "invert" would be misbehaving,
but then you can anyway get the inverse as
v##diag(1./sv)##transpose(u).

ralf

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[Message index]

		Re: problem inverting matrix By: Ralf Flicker on Mon, 06 January 2003 12:10
		Re: problem inverting matrix By: Lars Schmidt on Mon, 06 January 2003 10:18
		Re: problem inverting matrix By: Paul Van Delst[1] on Mon, 06 January 2003 09:20
		Re: problem inverting matrix By: Lars Schmidt on Mon, 06 January 2003 07:49
		Re: problem inverting matrix By: David Fanning on Mon, 06 January 2003 07:08

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