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Nonlinear Fit

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59855] Nonlinear Fit
  • From: Kevin Towles <kbt22 at drexel.edu>
  • Date: Wed, 24 Aug 2005 06:30:23 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I am trying to do a nonlinear  fit of a function that contains a  
numerical integration.  My problem is that when I call the nonlinear  
fit, it tries to evaluate within the nonlinear fit call.  For example:

Test=Function[{x1,a1},
NIntegrate[a*x^3,{x,0,100}]
];

NonlinearFit[data,Test[x,a],x,{a,0,1}]

Here I have a variable x and a parameter a.   This would return an  
NIntegrate error saying that 'NIntegrate is not numerical at x={50.}'  
because there is an unknown, a, in the integration.

It tries this a couple times and then shuts off the functioning of  
NIntegrate for further calculations, making fitting this impossible.   
Is there a way to fit this kind of situation without having the test  
function evaluate prior to fitting occuring?

Thanks for any help,

Kevin Towles



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