Re: FinFit question

*To*: mathgroup at smc.vnet.net*Subject*: [mg54834] Re: [mg54816] FinFit question*From*: DrBob <drbob at bigfoot.com>*Date*: Fri, 4 Mar 2005 05:07:33 -0500 (EST)*References*: <200503030329.WAA21066@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

Do it this way: << Statistics`NonlinearFit` points = {{23400, 273.2}, {6800, 298.2}, {2400, 323.2}}; T[R_] = NonlinearFit[points, B/(Log[R] - logRo), {R}, {B, logRo}] T /@ points[[All, 1]] 4021.0588923624114/ (4.658619219272381 + Log[R]) {273.186, 298.225, 323.188} The original form (using Ro) is asking for trouble because you have (in your mind alone) an assumption that Ro>0. There is no such restriction on logRo. Bobby On Wed, 2 Mar 2005 22:29:06 -0500 (EST), Zsolt Regály <zs.regaly at icsip.elte.hu> wrote: > Hi > > I have used Mathematica 4.2 to solve this problem > > points = {{23400, 273.2}, {6800, 298.2}, {2400, 323.2}}; > T[R_] = NonlinearFit[points, B/Log[R/Ro], {R}, {B, Ro}]; > > wihich gives the result as > > 4021.05/Log[105.49 R] > > > That is a good result, but when I try to do the same in Mathematica 5.0 > I get error messaeges and an other solutions, which is surely bad > 1556.90/Log[-0.014 R] > > Why doesn't work FindFit for this function in Mathematica 5.0 > > Regards, > Zsolt Regaly (zs.regaly at astro.elte.hu) > > > > -- DrBob at bigfoot.com www.eclecticdreams.net

**References**:**FinFit question***From:*Zsolt Regály <zs.regaly@icsip.elte.hu>