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simultaneous fit of multiple data sets

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  • Subject: [mg48024] simultaneous fit of multiple data sets
  • From: Mary Beth Mulcahy <Mary.Mulcahy at>
  • Date: Fri, 7 May 2004 04:29:42 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

I am a chemist using a technique called dielectric spectroscopy, the important
point is that I get 3 sets of data from a single sample by using different
frequencies.  The model to fit the data is as follows:

model = Table[{t, .000057 + Sum[(.08/t)*w*Exp[en/(k*t)]/(1 + w^2*Exp[en/(k*t)]
^2*1/Cosh[a/(k*t)]^2*Gaussian[en, ampl, x0, sigma], {en, 4, 12, .1}]}, {t, 85,

I would like to use Mathematica to simultaneously fit for ampl, xo, sigma, and
a for the three data sets since the parameters should remain constant over the
differ frequencies (w).  I am having trouble just getting one frequency to
fit, but can't decide even if I get that to work, that Mathematica will be
able to fit three separate curves simultaneously.  I do have the additional
Experimental Data Analysis (EDA) package.  I can (and have) done this more or
less by a visual trial and error, but it would be nice to get a chi-squared
value for my results and to have this be more automated for the future.

Thank you,

Mary Beth Mulcahy

University of Colorado

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