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MathGroup Archive 2007

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Re: Bounding Parameters used in FindFit[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75217] Re: Bounding Parameters used in FindFit[]
  • From: dh <dh at metrohm.ch>
  • Date: Sat, 21 Apr 2007 23:02:33 -0400 (EDT)
  • References: <f09fkk$j8$1@smc.vnet.net>


Hi Joshua,

consider the surface of fit-residuals. If this surface has one unique 

minimum, you can either give P1 a fixed value or you can use Minimize or 

NMinimize to make a constrained fit.

On the other hand, if the surface has several minima, you may force 

FindFit to find a minimum that you suits you better by specifying a 

start value for e.g. P1 like: {P1,1}.

hope this helps, Daniel



Joshua LaForge wrote:

> Is there a method to limit (bound) the search for a least-squares fit

> with FindFit[] in Mathematica 5.2?

> 

> For example I am using FindFit[] to fit a decaying exponential of the

> form P1 * Exp[-t/P2] + P3.  I know from the experiment that P3 is

> smaller than the value Mathematica continues to find for that

> parameter.  It would be great if there was a way to bound the search

> for P3 to help Mathematica properly optimize P1 and P2.

> 

> Joshua LaForge

> 

> 




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