Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2001
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Getting parameters from Fit[]..

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27101] Re: [mg27055] Getting parameters from Fit[]..
  • From: BobHanlon at aol.com
  • Date: Sun, 4 Feb 2001 02:58:27 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Needs["Statistics`LinearRegression`"];

data={{0.055,90},{0.091,97},{0.138,107},{0.167,124},{0.182,142},{0.211,
        150},{0.232,172},{0.248,189},{0.284,209},{0.351,253}};

funcs = {1, x, x^2};

bfp=(BestFitParameters /. 
        Regress[data, funcs, x, RegressionReport -> BestFitParameters]);

bfp.funcs == Fit[data, funcs, x]

True

funcs = {1, x^2};

bfp=(BestFitParameters /. 
        Regress[data, funcs, x, RegressionReport -> BestFitParameters]);

bfp.funcs == Fit[data, funcs, x]

True

Bob Hanlon

In a message dated 2001/2/3 5:25:07 AM, harderm at ucs.orst.edu writes:

>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?
>


  • Prev by Date: Re: Parametric Plot
  • Next by Date: Re: Getting parameters from Fit[]..
  • Previous by thread: Re: Getting parameters from Fit[]..
  • Next by thread: Re: Getting parameters from Fit[]..