When performing an extended LL fit the extended fit parameter does not appear as additional parameter in the fit result. I would expect this to be the case for a proper extended ML fit?

Here’s the code snippet, set up following what suggested in https://root.cern.ch/root/htmldoc/guides/users-guide/FittingHistograms.html

//----------------------------------------------------------------------------

ROOT::Math::MinimizerOptions myMinimizerOptions;

ROOT::Fit::Fitter myFitter;

ROOT::Math::WrappedMultiTF1 myFitFunction(*FitFunction, FitFunction->GetNdim() );

myFitter.SetFunction(myFitFunction,false);

ROOT::Fit::FitConfig myFitConfig=myFitter.Config();

myMinimizerOptions.SetPrintLevel(4);

myFitConfig.SetMinimizerOptions(myMinimizerOptions);

printf(“Now going for the actual fit call…\n”);

myFitter.Fit(*UnBinnedData,true);

myFitter.GetMinimizer()->PrintResults();

//----------------------------------------------------------------------------

Where FitFunction is a unit-normalized exponential parameterised as a function of the exponential slope a in e^a*x

The result of the parameters printout:

FCN=22743.4 FROM MIGRAD STATUS=CONVERGED 14 CALLS 15 TOTAL

EDM=1.616e-11 STRATEGY= 1 ERROR MATRIX ACCURATE

EXT PARAMETER STEP FIRST

NO. NAME VALUE ERROR SIZE DERIVATIVE

1 ExponentialConstant 9.99163e-04 1.41049e-04 1.46889e-05 2.85005e-02

ERR DEF= 0.5

is this the intended behaviour? Is the fitter misconfigured in the above example?

thank you!

Alex

*ROOT Version:* 6.14/06

*Platform:* Mac OS 10.14.4

*Compiler:* Not Provided