Nonlinear fit
- To: mathgroup at smc.vnet.net
- Subject: [mg41096] Nonlinear fit
- From: "Gustavo Seabra" <seabra at ksu.edu>
- Date: Fri, 2 May 2003 03:59:34 -0400 (EDT)
- Organization: Kansas State University
- Sender: owner-wri-mathgroup at wolfram.com
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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