       Re: Fittings 2 sets of equations and 2 data sets with nonlinearmodelfit

• To: mathgroup at smc.vnet.net
• Subject: [mg121709] Re: Fittings 2 sets of equations and 2 data sets with nonlinearmodelfit
• From: Daniel Lichtblau <danl at wolfram.com>
• Date: Mon, 26 Sep 2011 20:06:02 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

```On 09/26/2011 03:14 AM, JamesE wrote:
> Hi,
>
> My names is James Ellison; and I have 2 nonlinear equations of the type:
>
> y=x+a*x^2+b*x^3 and y=a*x^3+b*x^5 with the real valued parameters a and b for both equations.
>
> I further have 2 data sets
>
> data for y and
> data for y
>
> I can use NonlinearModelFit in order to fit each data[i] set to its function y[i] and get good fits. But the parameters a and b should be the same.
>
> How can I create a simple code with Mathematica, so that I can do a simultaneous fit resulting in the parameters a and b to be the same.
>
> I am a Mathematica beginner and would be pleased, if someone could answer my question for beginners.
>
> Best regards, James

rough idea is to contsruct one model that switches between two forms
based discrete values of a new dimension parameter. Could be, say, 1 for
the first data set and 2 for the second one.

http://forums.wolfram.com/mathgroup/archive/2004/Oct/msg00031.html

http://forums.wolfram.com/mathgroup/archive/2006/Apr/msg00011.html

http://forums.wolfram.com/mathgroup/archive/2006/Apr/msg00020.html

http://forums.wolfram.com/mathgroup/archive/2010/Apr/msg00280.html

Daniel Lichtblau
Wolfram Research

```

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