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Re: mpcurvefit vs. a matlab fitting technique [message #61574]

Wed, 23 July 2008 21:07

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

sheilakanani@googlemail.com writes:

>> But if I change the input even slightly eg [9.4,0.24,0.77,-1.5]
>> I get totally different values out, eg [7.7098139, 0.19333284,
>> 0.60223838, -0.85758867]
>>
>
> Sorry, typo, this should read:
>
> But if I change the input even slightly eg [9.44,0.24,0.77,-1.5]
> I get totally different values out, eg [7.7098139, 0.19333284,
> 0.60223838, -0.85758867]

This person also sent me a private email, which I
replied to. Here is what I wrote:

Without more information, I can offer only a few suggestions. First
of all, the different fit parameter sets you described *may* be a good
fit. MPFIT stops iterating when it achieves it tolerances, and cant
know how the previous fit did. If both are good fits, then that tells
you something about your model. Some other ideas about parameter
convergence are here:

http://cow.physics.wisc.edu/~craigm/idl/fitqa.html#parstep

It may be that you need to set PARINFO.STEP for some parameters.

Craig

--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: mpcurvefit vs. a matlab fitting technique By: Craig Markwardt on Wed, 23 July 2008 21:07
		Re: mpcurvefit vs. a matlab fitting technique By: R.G. Stockwell on Tue, 22 July 2008 09:46
		Re: mpcurvefit vs. a matlab fitting technique By: Vince Hradil on Tue, 22 July 2008 06:12
		Re: mpcurvefit vs. a matlab fitting technique By: sheilakanani on Tue, 22 July 2008 03:55

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