#include"TF1.h"
using namespace RooFit;
void roomodel(){
TFile *myfile =new TFile("sel_BsToPhiMuMu_OfficialMC_signal_2016Mini_Presel_v2_mc.lite_cut_bdt_s86000000.root","READ");
TTree *mytree =(TTree*)myfile->Get("tree"); //we want to read out the tree,so we have to make a reference
double Bmassi;
mytree->SetBranchAddress("Bmass",&Bmassi);

int entries = mytree->GetEntries();
cout<<entries<<endl;
TH1F *hist = new TH1F("hist","Bmass",401,4.6,5.7);

for (int i=0;i<entries;i++){
    mytree->GetEntry(i);
    // cout<<Bmass<<endl;
    hist->Fill(Bmassi);
}
RooRealVar x("x", "x", 4.6,5.7);
RooDataHist dh("dh", "dh", x, Import(*hist));
 RooPlot *frame = x.frame();
   dh.plotOn(frame);
   RooRealVar mean("mean", "mean", 0, 0, 10);
   RooRealVar sigma1("sigma1", "sigma2", 3, 0.001, 5);
   RooRealVar sigma2("sigma2", "sigma2", 3, 0.001, 5);
   RooGaussian sig1("sig1", "gauss sig1", x, mean, sigma1);
   RooGaussian sig2("sig2", "gauss sig2", x, mean, sigma2);
  //  exponential function 
  RooRealVar a("a","coeff of x in exp",0.01,0.,0.5);
  RooExponential sig3("sig3","exponential sig",x,a);

  RooRealVar fsig1("fsig1","sig1 fraction",0.5,0.,1.) ;
RooRealVar fsig2("fsig2","sig2 fraction",0.2,0.,1.) ;

  RooAddPdf model("model","model",RooArgList(sig1,sig2,sig3),RooArgList(fsig1,fsig2)); ;
   model.fitTo(dh,"R");
   double chiSquare = frame->chiSquare(2);
   
   model.plotOn(frame);
   model.plotOn(frame, Components(sig1),LineStyle(kDashed)) ;
   model.plotOn(frame, Components(sig2),LineStyle(kDashed)) ;
   model.plotOn(frame, Components(sig3),LineStyle(kDashed)) ;
   frame->Draw();
  frame->chiSquare() ;
   cout<<"Chi sq val = "<<chiSquare<<std::endl;
   
}