void combinedFit() {
TH1D * hB = new TH1D("hB","histo B",100,0,100);
TH1D * hSB = new TH1D("hSB","histo S+B",100, 0,100);
TF1 * fB = new TF1("fB","expo",0,100);
fB->SetParameters(1,-0.05);
hB->FillRandom("fB");
TF1 * fS = new TF1("fS","gaus",0,100);
fS->SetParameters(1,30,5);
hSB->FillRandom("fB",2000);
hSB->FillRandom("fS",1000);
// perform now global fit
TF1 * fSB = new TF1("fSB","expo + gaus(2)",0,100);
ROOT::Math::WrappedMultiTF1 wfB(*fB,1);
ROOT::Math::WrappedMultiTF1 wfSB(*fSB,1);
ROOT::Fit::DataOptions opt;
ROOT::Fit::DataRange rangeB;
// set the data range
rangeB.SetRange(10,90);
ROOT::Fit::BinData dataB(opt,rangeB);
ROOT::Fit::FillData(dataB, hB);
ROOT::Fit::DataRange rangeSB;
rangeSB.SetRange(10,50);
ROOT::Fit::BinData dataSB(opt,rangeSB);
ROOT::Fit::FillData(dataSB, hSB);
ROOT::Fit::Chi2Function chi2_B(dataB, wfB);
ROOT::Fit::Chi2Function chi2_SB(dataSB, wfSB);
GlobalChi2 globalChi2(chi2_B, chi2_SB);
ROOT::Fit::Fitter fitter;
const int Npar = 6;
double par0[Npar] = { 5,5,-0.1,100, 30,10};
// create before the parameter settings in order to fix or set range on them
fitter.Config().SetParamsSettings(6,par0);
// fix 5-th parameter
fitter.Config().ParSettings(4).Fix();
// set limits on the third and 4-th parameter
fitter.Config().ParSettings(2).SetLimits(-10,-1.E-4);
fitter.Config().ParSettings(3).SetLimits(0,10000);
fitter.Config().ParSettings(3).SetStepSize(5);
fitter.Config().MinimizerOptions().SetPrintLevel(0);
fitter.Config().SetMinimizer("Minuit2","Migrad");
// fit FCN function directly
// (specify optionally data size and flag to indicate that is a chi2 fit)
fitter.FitFCN(6,globalChi2,0,dataB.Size()+dataSB.Size(),true);
ROOT::Fit::FitResult result = fitter.Result();
result.Print(std::cout);
TCanvas * c1 = new TCanvas("Simfit","Simultaneous fit of two histograms",
10,10,700,700);
c1->Divide(1,2);
c1->cd(1);
gStyle->SetOptFit(1111);
fB->SetFitResult( result, iparB);
fB->SetRange(rangeB().first, rangeB().second);
fB->SetLineColor(kBlue);
hB->GetListOfFunctions()->Add(fB);
hB->Draw();
c1->cd(2);
fSB->SetFitResult( result, iparSB);
fSB->SetRange(rangeSB().first, rangeSB().second);
fSB->SetLineColor(kRed);
hSB->GetListOfFunctions()->Add(fSB);
hSB->Draw();
}
