Re: Exponential fit question.
- To: mathgroup at smc.vnet.net
- Subject: [mg28020] Re: Exponential fit question.
- From: Ignacio Rodriguez <ignacio at sgirmn.pluri.ucm.es>
- Date: Wed, 28 Mar 2001 02:40:51 -0500 (EST)
- References: <99pdg6$lft@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Fit will try a fit in the following way:
Fit[data,{a(x),b(x)},x] will fit data to A a(x) + B b(x), where a(x) and
b(x) are the functions you supply and A and B are two fit parametes.
In your case, Fit[data,Exp[x],x] will fit data to A Exp[x], which is
clearly not the case for your data.
You can try a nonlinear fit defined in `Statistics`NonlinearFit, but I
would suggest taking the logarithm of your y data and trying a linear
fit.
Try this:
data={{50,22},{64,62},{78,122},{93,269},{107,414},{122,507},{136,597}}
logdata=Table[{Part[data,i,1],Log[Part[data,i,2]]},{i,1,7}]
Exp[Fit[logdata,{1,x},x]]
Hope it helps
> hello.
>
> I was wondering if someone could help me with the following problem.
>
> I am trying to perform an exponential fit to the following data
> {{x,y}}
>
> data
> ={{50,22},{64,62},{78,122},{93,269},{107,414},{122,507},{136,597}}
>
> Fit[data,Exp[x],x]
>
> what I get is
>
> 1.94272422061017735^-63 *E^x Which is not correct.
>
> With Excel I get 7.5*E^0.0034x which is correct.
>
> How can I do this with Mathematica ?
>
> Thanks.
> -Joseph.
--
Ignacio Rodriguez Ramirez de Arellano
Unidad de RMN
Universidad Complutense
Paseo Juan XXIII, 1
Madrid 28040, Spain
Tel. 34-91-394-3288
Fax 34-91-394-3245
e-mail: ignacio at sgirmn.pluri.ucm.es
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