testRooHistPdf.C

double testRooHistPdf(){
    TFile * inputFile = TFile::Open("./testShapes.root");

    TH1F * dataHist = (TH1F *)inputFile->Get("Signal/data_obs");
    TH1F * zinv = (TH1F *)inputFile->Get("Signal/Zinv");
    TH1F * ttw = (TH1F *)inputFile->Get("Signal/Ttw");
    TH1F * qcd = (TH1F *)inputFile->Get("Signal/Qcd");
    TH1F * sigHist = (TH1F *)inputFile->Get("Signal/sig");

    TH1F * totalHist = (TH1F *)zinv->Clone("total");
    totalHist->Add(ttw);
    totalHist->Add(qcd);

    RooRealVar r("r","r",1,-5,5);
    RooRealVar  x("dummy","Dummy real var",1);

    RooRealVar nsig("nsig","number of signal events",5) ;
    RooRealVar nbkg("nbkg","number of background events",30) ;

    RooDataHist data("data","data",x,dataHist);
    RooDataHist bkgDataHist("bkgDataHist","bkgDataHist",x,totalHist);
    RooDataHist sigDataHist("sigDataHist","sigDataHist",x,sigHist);

    RooHistPdf bkg("bkg","bkg",x,bkgDataHist,0);
    RooHistPdf sig("sig","sig",x,sigDataHist,0);

    RooExtendPdf esig("esig","extended signal p.d.f",sig,nsig) ;
    RooExtendPdf ebkg("ebkg","extended background p.d.f",bkg,nbkg) ;
    //
    // RooProduct sigStrength("rsig","sig * r",RooArgSet(r,esig));

    RooAddPdf model("model","sig +bkg",RooArgSet(esig,ebkg));


    fitResult = model.fitTo(data);
    xframe = x.frame();
    data.plotOn(xframe);
    model.plotOn(xframe, RooFit::VisualizeError(*fitResult));
    data.plotOn(xframe); // plot again so that it is on top of the errors
    model.plotOn(xframe, RooFit::LineColor(4));
    model.plotOn(xframe, RooFit::Components("esig"), RooFit::LineColor(1));
    model.plotOn(xframe, RooFit::Components("ebkg"), RooFit::LineColor(2));
    xframe->Draw();
    return 0;


}