Hi Vitor,
I wonder why you want to fix the step size of the parameter search ?
An intelligent minimizing algorithm will change its step size !
Eddy
--- Vitor de Souza <vitor@astro.iag.usp.br> wrote:
> Dear all,
> I would like to fix the step size of a parameter in a fit.
> I am using the code below:
>
> static double vstart[npar]; // inital point
> static double step[npar]; // step size
> TMinuit * theMinuit = new TMinuit(npar); // 3 parameter fit
> step[0]=10.0;
> step[1]=100.0;
> step[2]=1.0;
> theMinuit->mnparm(0,"n",vstart[0],step[0],0,0,ierflag);
> theMinuit->mnparm(1,"x",vstart[1],step[1],500,1000,ierflag);
> theMinuit->mnparm(2,"x0",vstart[2],step[2],0,0,ierflag);
> theMinuit->mnexcm("SET ERR", arglist,1,ierflag);
> double arglist[npar];
> int ierflag =0;
> arglist[0] = 1500;
> arglist[1] = 1.;
> theMinuit->mnexcm("MIGRAD", arglist , 2, ierflag);
>
> As far as I understood from the manual, the values set as step[] in
> the
> command theMinuit->mnparm( ) is the size of only the first step in
> the
> fit procedure.
> Is there a way to fix the step size for the hole fit procedure ?
> Thank you,
> Vitor
>
>
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