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Re: SVDFIT Problems [message #32017 is a reply to message #31937]

Tue, 03 September 2002 08:20

Chris Torrence
Messages: 5
Registered: March 2001

Junior Member

Hi Bill,

Actually, the SVDFIT code *does* use THRESH = TOL*wmax. If you look
carefully at the IDL code, around line 249, there is the following line:

small=WHERE(variance LE max(variance)*thresh, cc)

(The variable name "thresh" was an unfortunate choice, and should really
have been "tol".)

Internally, the C code is identical to the Numerical Recipes code, except
for the TOL value, which is 1e-9 for both single and double precision. We
could consider adding a TOL keyword to the SVDFIT function, which would
allow the user to change this default.

Cheers,

Chris
Research Systems, Inc.

"Bill" <wclodius@lanl.gov> wrote in message
news:3D6F97ED.C81C6C00@lanl.gov...
> In my occaisional attempts to use SVDFIT I have had problems in that it
> reports singular solutions when other fitting routines, e.g., REGRESS,
> have had not problems. The obvious source of the problems is that within
> the routine the line
>
> THRESH = 1.0E-9
>
> does not correspond to the definition in Numerical Recipes
>
> THRESH = TOL*wmax
>

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[Message index]

		SVDFIT Problems By: William Clodius on Fri, 30 August 2002 09:06
		Re: SVDFIT Problems By: Chris Torrence on Tue, 03 September 2002 08:20
		Re: SVDFIT Problems By: William Clodius on Thu, 05 September 2002 10:26
		Re: SVDFIT Problems By: William Clodius on Fri, 06 September 2002 10:08
		Re: SVDFIT Problems By: William Clodius on Tue, 10 September 2002 15:42
		Re: SVDFIT Problems By: William Clodius on Thu, 05 September 2002 16:43
		Re: SVDFIT Problems By: James Kuyper on Thu, 05 September 2002 13:15

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