fitTo vs. interactive minimization

Roofit and RooStats
#1

Hi everybody,

shouldn’t there be no difference between calling the fitTo method

model.fitTo(data);

and doing an interactive minimization like

RooAbsReal* nll = model.createNLL(data);

RooMinuit m(*nll);

m.migrad();
m.hesse();
m.minos();

since fitTo performs a maximum likelihood fit “executed through the MINUIT commands MIGRAD, HESSE and MINOS in succession”. When I do both procedures I get different results.

Thanks!
Cheers,
dWade

#2

The first one should be equivalent to the second one without hesse and minos. If you want to run those in fitTo, I think you need to pass the option explicitly in the fitTo command.

Lorenzo

#3

Hi,

ok, actually I thought so. But in the documentation of RooAbsPdf it is said that fitTo calls migrad hesse and minos by default. (root.cern.ch/root/html/RooAbsPdf … sPdf:fitTo)
Anyway, I checked it and like you said fitTo yields the same results as running migrad only.

Cheers,
dWade