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MathGroup Archive 2004

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Constraints to parameters in FindFit?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51200] Constraints to parameters in FindFit?
  • From: Jill Foley <efoley at princeton.edu>
  • Date: Fri, 8 Oct 2004 02:54:48 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi All,

I am using FindFit to fit a series of peaks to some data. I would like 
to be able to constrain some of the parameters of my fit to correspond 
to physical reality. For example, some peaks should have a negative 
amplitude, others positive, where the amplitudes are the parameters 
that Mathematica is finding in FindFit. The peaks are all very near 
each other, so without any constraint, it is making the wrong ones 
negative. I'd like to specify that a given parameter should always be 
negative. I am already giving an initial guess of the proper sign, but 
it doesn't fix the problem.

Please advise - Thanks!

Jill.


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