Re: Fit in Excel Mathlink
- To: mathgroup at smc.vnet.net
- Subject: [mg5005] Re: Fit in Excel Mathlink
- From: vvs124 at rsphy1.anu.edu.au (Victoria Steblina)
- Date: Sat, 19 Oct 1996 02:25:50 -0400
- Organization: Australian National University
- Sender: owner-wri-mathgroup at wolfram.com
In article <53sm1g$3nj at dragonfly.wolfram.com> Harald Berndt <haraldb at nature.berkeley.edu> writes: > Mark Dowell wrote: > > > > Dear All, > > > > Can anyone hellp I'm trying to fit some data under Excel with the Mathlink > > addon the fitting equation is > > > > y=a(0)*Exp(-a(1)*(x-400))+a(2) > > > > I just need value for best fit in a(0),a(1),a(2). for a given range in Excel > > cells can anyone help with the syntax > > Well, the Standard Package "NonlinearFit" is supposed to do it, but I > had very little luck with problems similar to yours. Maybe things will > improve in Version 3.0 Same here. I did a lot of NonlinearFit with mathematica for 3 parameter models... It is VERY frustating because you can't cover ALL the parameter's space, and you never really know HOW to reach the global minimum of ChiSquared. The only thing I can tell you, and it won't help much, I'm afraid, is that you MUST have very good initial guess for your parameters. One of the best methods, as far as I know, is the use of genetic algorithm to obtain initial values. Best of luck Vicki ________________________ vvs124 at rsphy1.anu.edu.au