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Re: alternative to CURVEFIT function [message #84356 is a reply to message #84355]

Thu, 30 May 2013 12:09

Meg
Messages: 7
Registered: May 2013

Junior Member

On Wednesday, May 29, 2013 9:39:08 PM UTC-4, Craig Markwardt wrote:
> On Wednesday, May 29, 2013 11:19:27 AM UTC-4, fd_...@mail.com wrote:
>
>> I was wondering if anyone knows an alternative function of CURVEFIT. If I am not mistaken the CURVEFIT uses the Levenberg-Marquart algorithm. I need to use a different algorithm which provides a numerical solution to the problem of minimising a function, generally non-linear.
>
>>
>
>> Nelder–Mead method and Newton-Raphson are some choices but I was wondering if there is a function in IDL like the CURVEFIT.
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>
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> Adding to what the other posters said...
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>
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> If you can any way express your function as the sum of squared residuals, then you should try to use the MPFIT family of functions. It is far more stable than CURVEFIT.
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> Note that you can sometimes bend the rules. If your optimization function is the sum of *somethings*, then often you can rewrite the somethings as (somethings elses)^2. As long as (something else) is signed, you can use MPFIT.
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> If you really need general function minimization, then yes you can try my TNMIN. If your user function is smooth then it will find a minimum with a Newton-type method.
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> Craig
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> http://cow.physics.wisc.edu/~craigm/idl/fitting.html

Hi,

I'm trying to learn more about MPFIT too. I don't understand how to use the routines once I have downloaded the .pro files (new programer). I'm just not sure where to put the files so that IDL reads MPFITFUN as a routine and not a variable. Can you point me to a resource that will help?

- Meg

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[Message index]

		Re: alternative to CURVEFIT function By: Craig Markwardt on Thu, 30 May 2013 21:56
		Re: alternative to CURVEFIT function By: Craig Markwardt on Thu, 30 May 2013 21:48
		Re: alternative to CURVEFIT function By: David Fanning on Thu, 30 May 2013 16:37
		Re: alternative to CURVEFIT function By: wlandsman on Thu, 30 May 2013 16:05
		Re: alternative to CURVEFIT function By: David Fanning on Thu, 30 May 2013 12:25
		Re: alternative to CURVEFIT function By: Meg on Thu, 30 May 2013 12:09
		Re: alternative to CURVEFIT function By: Russell Ryan on Thu, 30 May 2013 11:47
		Re: alternative to CURVEFIT function By: Craig Markwardt on Wed, 29 May 2013 18:39
		Re: alternative to CURVEFIT function By: Russell Ryan on Wed, 29 May 2013 13:15
		Re: alternative to CURVEFIT function By: David Fanning on Wed, 29 May 2013 08:38
		Re: alternative to CURVEFIT function By: Meg on Thu, 30 May 2013 12:05
		Re: alternative to CURVEFIT function By: Russell Ryan on Fri, 31 May 2013 05:59

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