Getting parameters from Fit[]..
- To: mathgroup at smc.vnet.net
- Subject: [mg27055] Getting parameters from Fit[]..
- From: "Mark Harder" <harderm at ucs.orst.edu>
- Date: Sat, 3 Feb 2001 04:58:52 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
I am doing a linear fit to obtain parameters for use in a larger,
iterative procedure (a separable linear-nonlinear data fitting
algorithm), and I'm trying to use Fit[] to do this. Unfortunately, Fit
does not return parameters by themselves, just the linear combination of
my basis functions(which are much more complicated than the usual
examples given in the documentation) weighted by the parameters. I have
tried various things, like using Regress instead of Fit, but that prints
out at least a written report of the parameters every time it is
invoked, which will make for a very cluttered output when included in
the larger problem I am trying to solve. I suppose I can find a method
to isolate just the parts of the output of Fit that contain the
parameters and process them to get the parameters, but that seems
awkward and might introduce numerical errors. I've looked at the
MathGroup archives and found only 1 response to this question in the
past, which was "Sorry, dont know how to do that. why don't you use
Regress?".
Doesn't Mathematica provide any simple method for recovering just
the parameter vector from a linear fit? If it doesn't, perhaps it ought
to. Alternatively, is there some way to get Regress to provide the
BestFitParameters rules without printing them out? Or, is there some
*simple* and accurate way of getting the parameters from the Fit output
as is?
-mark harder
harderm at ucs.orst.edu