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MathGroup Archive 1992

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non-linear fitting of data

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: non-linear fitting of data
  • From: wilson%scuche.hepnet at lbl.gov
  • Date: Fri, 29 May 92 09:59:36 PDT

                                        Univ of South Carolina, 29-MAY-1992

    The Fit function as described in the MMA book only does linear fitting,
meaning that it fits only to a linear combination of user-supplied
functions.  I want to do nonlinear fitting, meaning that I want to give MMA
a function of x and also a function of adjustable parameters, and have MMA
find the best values for those parameters, not just some multiplicative
factor for the function.  Does anyone know how I can do that with Fit, or
if there is a nice package I can use?

I tried the following:

Fit[ wire5k, {1/(c (1 + ((x-d)/c)^2))}, {x,c,d} ]

The idea is that I want x,c and d to all vary.  The red error msg I got
was:

Fit::arg: Fit has received {x, c, d} as argument.

                                   Scott





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