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MathGroup Archive 2006

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Re: NonlinearFit + Sums

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68799] Re: NonlinearFit + Sums
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 19 Aug 2006 00:41:03 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <ec3q7k$2fd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Lyta wrote:
> Hi,
> 
> I want to do a mulitdimensional nonlinear fitting and I'm not sure how to define the mathematica statement for that.
> 
> I have a matrix "data" of dimensions 140x37 that contains 36 samples of 140 functions. The 37th column contains the resulting value of a mapping of the type R36->R1. I want to calculate the parameter mu of a function that integrates over the samples - i posted a simplified version of the function below. My problem is, that I don't know what to write instead of x_i. For the second x_ it should be something like {x1, x2, x3, x4, ..., x36}. But the first x_i should be something like x[[i]] (this doesn't work ofc). How do i assign the data to the sum?
> 
> NonlinearFit[data, Sum[E^(mu)*x_i, {i, 1, 36}], x_i, {mu}]
> 
> I hope you can help :-)
> 

The following should do what your are looking for:

data = Table[Random[], {140}, {37}];
model = Plus @@ Table[E^mu*x[i], {i, 1, 36}]
Needs["Statistics`NonlinearFit`"]
NonlinearFit[data, model, Table[x[i], {i, 1, 36}], {mu}]

HTH,
Jean-Marc


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