Re: Can Fit give function coefficients?

*To*: mathgroup at smc.vnet.net*Subject*: [mg31139] Re: Can Fit give function coefficients?*From*: bap at roe.ac.uk (Brett Patterson)*Date*: Sat, 13 Oct 2001 02:47:04 -0400 (EDT)*References*: <9pu3u0$bc8$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I'd just like to summarise the feedback I've received so far, since I think this thread is probably thinning out now. Firstly, thank you everyone for responding to my question. I have great suggestions in particular from: Jens-Peer Kuska (kuska at informatik.uni-leipzig.de) --- using NumericQ and BobHanlon at aol.com (BobHanlon at aol.com) --- using NonlinearFit. Both are succinct and easy to implement, so I'm happy now! 8-) I'd also like to share the following that I received via private email from someone "Siegman" at Stanford: > Here's a pointer to an expanded version of the standard > Fit[] routine that > also gives the coefficients. > > http://www-ee.Stanford.EDU:80/~siegman/SimpleFit.txt This SimpleFit function actually does exactly what I was wanting, and it's fast! Finally, thank for your help Yas, from Melbourne, but for future reference, it's probably not a good idea to post Notebooks as attachments to group lists. Bye, Brett Patterson "Brett Patterson" <bap at roe.ac.uk> wrote in message news:<9pu3u0$bc8$1 at smc.vnet.net>... > I have a set of functions that I wish to fit to some data. > Is there a way to succinctly get Mathematica to give me > the coefficients of these functions in the fit. > > For example, say I have > f1[x_] := 2 x^2 > f2[x_] := 3 x^3 > > Normally, if I say: Fit[data, {1, f1[x], f2[x]}, x] > I get a result in the form: a1 + b1 x^2 + c1 x^3, > but I want a result of the form: a2 + b2 f1[x] + c2 f1[x]. > In this case, a2 = a1, b2 = b1/2, and c2 = c1/3. > > Is this possible? > > Regards, > Brett Patterson