NonLinearRegress question
- To: mathgroup at smc.vnet.net
- Subject: [mg12860] NonLinearRegress question
- From: Easan Siviniah <easan at mrl.ucsb.edu>
- Date: Wed, 17 Jun 1998 00:28:03 -0400
- Organization: University of California, Santa Barbara
- Sender: owner-wri-mathgroup at wolfram.com
Hi folks,
I'm writing some data fitting code on Mathematica that uses the add-on
package
'NonLinearRegress'. However I'm currently stumped because the model I
use
for fitting involves the use of conditional 'Ifs'. It seems that
Mathematica does not recoginise such a function as numerical.
Does Anyone have an idea of how to get round this. I've included a
typical
but simplified example below.
In[1] Clear[fun,t,x,y]
fun[t_,x_,y_]:=If[t<10,t^2 x + Log[t] y, t^3 x + Log[t] y]
data=Table[{t,N[fun[t,2,3]]},{t,1,21,2}] Out[1]
{{1,2.},{3,21.2958},{5,54.8283},{7,103.838},{9,168.592},{11,2669.19},{13,
4401.69},{15,6758.12},{17,9834.5},{19,13726.8},{21,18531.1}}
In[2] << Statistics`NonlinearFit`
NonlinearRegress[data,
N[func[t,a,b]] ,z, {{a,{-100,-101}},{b,{2,3}}},
RegressionReport -> BestFitParameters,
Method->FindMinimum,
ShowProgress -> True]
Out[2] NonlinearRegress::"nonnum": "The model is not numerical at
(******)
Check that all model parameters are included in the
parameter list.