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RE: Nonlinear fit

  • To: mathgroup at smc.vnet.net
  • Subject: [mg41116] RE: [mg41096] Nonlinear fit
  • From: "Yahoo" <stefanofricano at yahoo.it>
  • Date: Sat, 3 May 2003 03:30:25 -0400 (EDT)
  • In-reply-to: <200305020759.DAA15079@smc.vnet.net>
  • Reply-to: <fricano at dsfa.fisica.unipa.it>
  • Sender: owner-wri-mathgroup at wolfram.com

The problem is, probably, in the definitions of D[f[x],p1] and respect to p2
etc...
There are some e-mail on Mathgroup database about it, see them.



***********************************************
Stefano Fricano
Dip. di Scienze Fisiche ed Astronomiche
Universit\140 degli Studi
Via Archirafi, 36
Palermo 90123
Tel. +39 091 6234207
Fax  +39 091 6168461
*********************************************
 
->-----Original Message-----
->From: Gustavo Seabra [mailto:seabra at ksu.edu]
To: mathgroup at smc.vnet.net
->Sent: Friday, May 02, 2003 10:00 AM
->To: mathgroup at smc.vnet.net
->Subject: [mg41116] [mg41096] Nonlinear fit
->
->
->Hi all,
->
->I am trying to make a nonlinear fit to a function (f[x]) that is defined
->differently for different intervals, something like (it's
->abbreviated here,
->to give just the idea):
->    f[x_]:=g[x+a]/;x>k
->    f[x_]:=g[x+b]/;x<=k
->
->I know the function is ok because, if I set the parameters, I can plot it
->with no problem:
->    Plot[f[x]./{p1->p1_initial_value,p2->p2_initial_value,...},{x,x1,x2}]
->
->However, if I try to fit a data set to this function with NonlinearRegress
->or NonlinearFit:
->    NonlinearFit[data,f[x],x,{p1,p2,...}]
->
->I get:
->"NonlinearFit::nonum :
->    The model is not numerical at {p1->value,p2->value...,x->value}. Check
->that all model parameters are included in the parameter list."
->
->    Now, I'm sure I included all parameters. As I said, if I try to plot
->f[x], even with the parameters from this answer, it works fine. Also, if i
->use a different f[x], defined the same for all x, all works fine. Any
->suggestion on what am I doing wrong?
->
->    Thanks a lot,
->                        Gustavo Seabra.
->
->P.S. If anyone needs more detail, I can provide the notebook with
->everything
->in it. I just didn't want to post it here to avoid too long a post.
->
->
->
->


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