Re: NonlinearFit
- To: mathgroup at smc.vnet.net
- Subject: [mg42676] Re: NonlinearFit
- From: gohtk at rocketmail.com (goh tat kean)
- Date: Sun, 20 Jul 2003 06:20:54 -0400 (EDT)
- References: <bf5kgf$mhc$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Dear Roger,
Try to give initial start value to your parameters, for example:
{{c0, 2}, {c1, 1.5}, {c2, 2.2}}
This is my try.
<< Statistics`NonlinearFit`
ex[c0_, c1_, c2_, T4_] := 1/c0 + 1/(c1*Exp[-c2/(0.695 T4)])
Some dummy data.
tb1 = Table[{T4, ex[1, 1, 1, T4] + Random[]}, {T4, 0.1, 5, 0.1}];
NonlinearFit[tb1, ex[c0, c1, c2, T4], T4, {{c0, 2}, {c1, 1.5}, {c2,
2.2}}, ShowProgress -> True]
Good luck!
Regards,
tat kean
Roger Mason <rmason at sparky2.esd.mun.ca> wrote in message news:<bf5kgf$mhc$1 at smc.vnet.net>...
> NonlinearFit[dat, 1/c0 + 1/(c1*Exp[-c2/(0.695 T4)]), T4, {c0, c1, c2}]
> returns the error
>
> NonlinearFit::nonnum: "The model is not numerical at {c0->1, c1->1,
> c2->1, T4->14.}. Check that all model parameters are included in the
> parameter list.
>
> There are 3 parameters in the model and all three _are_ given in the
> parameters list. On calculating the value of the function with c0=1,c1=1,
> c2=1 the value 1.902 is returned. In what way is that 'non-numerical'?
>
> Thanks for your help,
> Roger Mason