Re: Bounding Parameters used in FindFit[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg75217] Re: Bounding Parameters used in FindFit[]*From*: dh <dh at metrohm.ch>*Date*: Sat, 21 Apr 2007 23:02:33 -0400 (EDT)*References*: <f09fkk$j8$1@smc.vnet.net>

Hi Joshua, consider the surface of fit-residuals. If this surface has one unique minimum, you can either give P1 a fixed value or you can use Minimize or NMinimize to make a constrained fit. On the other hand, if the surface has several minima, you may force FindFit to find a minimum that you suits you better by specifying a start value for e.g. P1 like: {P1,1}. hope this helps, Daniel Joshua LaForge wrote: > Is there a method to limit (bound) the search for a least-squares fit > with FindFit[] in Mathematica 5.2? > > For example I am using FindFit[] to fit a decaying exponential of the > form P1 * Exp[-t/P2] + P3. I know from the experiment that P3 is > smaller than the value Mathematica continues to find for that > parameter. It would be great if there was a way to bound the search > for P3 to help Mathematica properly optimize P1 and P2. > > Joshua LaForge > >