TVirtualFitter + Errors

ROOT
1

Hi, I’m fitting a function with TVirtualFitter and I need to include the errors for the points. How do I do it with TVirtualFitter? Where is the manual for that?
This is what I’m using.

TVirtualFitter::SetDefaultFitter(“Minuit”);
TVirtualFitter *fitter = TVirtualFitter::Fitter(0, 3);
fitter->SetFCN(myfcn);

fitter->SetParameter(0, “par1”, 0, 0.1, 0,0);
fitter->SetParameter(1, “par2”, 0, 0.1, 0,0);
fitter->SetParameter(2, “par3”, 0, 0.1, 0,0);
fitter->SetParameter(3, “par4”, 1, 0.1, 0,0);

Double_t arglist[1] = {0};
fitter->ExecuteCommand(“MIGRAD”, arglist, 0);

Cheers, Eric

2

HI,

if you are fitting directly with the TVirtualFitter you have to write yourself the function to minimize.
See for example how the fcn function is implemented in this tutorial

root.cern.ch/root/html/examples/Ifit.C.html

However, if you are fitting just data points with uncorrelated errors, I would recommend you to do it via the TGraphErrors class.

Best Regards

Lorenzo