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Mma: Using FindRoot in NonlinearRegress ?


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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