Hi Eddy,
I agree that a good minimizing algorithm change its step size.
However, because of physical constraints a given parameter may not be
allowed to assumed all values within a limit.
Suppose you want to fit a parameter which for physical reasons can only
assume integer values. In this case, one would like to fix the step
size to a integer value.
In my case I would like to have parameter 1 of the fit only assuming
mutiples of 100 in the interval between 500 and 1000.
Is that possible ?
Thanks,
Vitor
Edmond Offermann wrote:
>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
>>
>>
>>
>>
>
>
>
This archive was generated by hypermail 2b29 : Sun Jan 02 2005 - 05:50:10 MET