Hi,
I have the following problem with my chi2 fit. I define the chi2 as squared distance of point of a TGraph with a TF1 function f (normalized by the error) - as usual. The function f depends on a free parameter p. The function f for a specific value of p is calculated using points that are tabulated for several values of p. The precision of this table is 10-3 in p.
How can I tell the Minimizer to take only steps of this size in p? I tried putting the step size to 0.001
double step[4] = {0.001,0.01,0.01,0.01};
min->SetVariable(0,“parameter”,variable[0],step[0]);
but the Minimizer still tries to calculate the function for p values too fine for my interval. As a result, it does not find a different chi2 value for e.g p=0.800 and p=0.7999 and is confused.
The other settings are
const char * minName = “Minuit2”;
const char algoName = “” ;
int randomSeed = -1;
ROOT::Math::Minimizer min = ROOT::Math::CreateMinimizer(minName, algoName);
min->SetMaxFunctionCalls(1000000); // for Minuit/Minuit2
min->SetTolerance(0.01);
min->SetPrecision(0);
min->SetPrintLevel(1);
Thank you very much!