Mma: Using FindRoot in NonlinearRegress ?

• To: mathgroup at smc.vnet.net
• Subject: [mg8749] Mma: Using FindRoot in NonlinearRegress ?
• From: jost at no-junk-mail.fr (Christian Jost)
• Date: Sat, 20 Sep 1997 22:28:14 -0400
• Organization: Universite Paris-Sud XI
• Sender: owner-wri-mathgroup at wolfram.com

```Hello everybody,

I am trying to use the FindRoot function in NonlinearRegress: so far with
no result, but it may be a simple format problem. Has anybody been able to
do this?

Here is a concrete example:
there is some data={{x1,y1},{x2,y2},...}
and some model, say
y = FindRoot[a x + b Cos[x]==0,{x,{0,10}}][[1,2]]

Now I want to fit a and b to this model:

NonlinearRegress[data,
FindRoot[a x + b Cos[x]==0,{x,{0,10}}][[1,2]],
{x},
{{a,{2.0,1.9},0,Infinity},{b,{0.001,0.002},0,Infinity}},
Method->FindMinimum,
ShowProgress->True,
MaxIterations->20]

But this doesn't work, there is a lot of error output, mainly that
FindRoot didn't find anything. I suspect somehow the current parameters a
and b are not passed to FindRoot.
Any help will be much appreciated.

Thanks, Christian.

*********************************************************************
Christian Jost, Université Paris-Sud XI, Orsay, France

Please don't send any junk mail or advertisements. For personal mail please send to: Christian.Jost at epc.u-psud.fr

```

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