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NonlinearFit

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: NonlinearFit
  • From: 4_DKEFFORD at fair1.fairfield.edu
  • Date: 05 Mar 1993 14:17:31 -0500 (EST)

Hello everybody.

Thanks for all your responses- many of you suggested that I use the latest
version of NonlinearFit available as shareware. I git it running and was
able to get it to work for a parabolic and a linear fit with no problems.
However, when I try to do a double exponential fit, which is what I need to
do in the first place, I keep getting the following error:

NonlinearFit::baddata '1' is not a real matrix

I have really no idea why this happens- I'm simply using about 200 points 
generated from a known double exponential, which I created as follows:

silicon=Table[{x,f[x]},{x,-50,450,5}]

where f[x_]=-.2*Exp[-.01*x]+.1*Exp[-.05*x]

Then I run the following:

NonlinearFit[silicon,a*Exp[-b*x]+c*Exp[-d*x],{a,b,c,d},x]

As far as I can see, I do not have any syntax errors or anything else that
springs to the imagination. Any ideas??

I can be reached at either:

4_dkefford at fair1.fairfield.edu      or
dkefford at delphi.com

Thank for your time.

Dan Kefford





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