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Re: Lorentzian on a baseline

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89194] Re: [mg89178] Lorentzian on a baseline
  • From: Darren Glosemeyer <darreng at wolfram.com>
  • Date: Thu, 29 May 2008 07:02:24 -0400 (EDT)
  • References: <200805280845.EAA27166@smc.vnet.net>

fred.engles at gmail.com wrote:
> I'm trying to fit a Lorentzian subtracted from a constant baseline,
> using findfit.
>
>  FindFit[rawdata, m1 - m2/((x - m3)^2 + m2^2), {m1, m2, {m3, 250}}, x,
>   MaxIterations -> 10000]
>
> Isn't working - either a totally flat horizantal line, or the
> subtracted 'Lorentzian' looks almost delta-function sharp. Help?
> Thanks!
>
> P.S. Does Experimental Data Analyst work with 6.0.1 (Mac)?
>   

Without a reproducible example, it's not possible to say for certain 
what the problem is. My first guess would be that the default parameter 
starting value of 1 is not good for m1 or m2 and that starting values 
should be specified for those parameters.

Darren Glosemeyer
Wolfram Research


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