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MathGroup Archive 2005

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Re: nonlinear fit question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60834] Re: nonlinear fit question
  • From: dh <dh at metrohm.ch>
  • Date: Fri, 30 Sep 2005 03:57:04 -0400 (EDT)
  • References: <dhgepn$1rd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Kevin
you are confusing range and starting values. What you spezify are 
starting values, see the documentation.
To ensure convergence to the minimum you want, You can either give 
better starting values (e.g. decrease xmax-xmin) or use another function 
like FindMinimum, where you can specify the range
sincerely, Daniel

Kevin Towles wrote:
> I am trying to do a nonlinear fit using a model I have developed.  My  
> problem is that my model is discontinuous and I only want to allow  
> the NonlinearFit function to search a range for the value of one of  
> the parameters. The actual implementation would be something like:
> 
> NonlinearFit[data,Model[xVar,yParam],xVar,yParam]
> 
> but I want yParam to be confined to a range as: ymin <= yParam <= ymax
> 
> I tried using NonlinearFit[data,Model[xVar,yParam],xVar,{yParam, 
> {ymin,ymax}}] but the function is obviously searching outside this  
> range.  I know there is a good fit in the range that I am specifying,  
> so I don't know why it insists on searching outside the start  
> values.  Is there a way to confine my yParam?
> 
> Any help is greatly appreciated.
> 
> Kevin Towles
> 


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