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