//IMP:::This macro is for creating a histogram from data

void normalized_roofit_test() {
using namespace RooFit;

//This is the method for unbinned fitting, for binned fitting histogram and rooDatahist are used.
RooRealVar x("x", "x",3,3.2);
RooDataSet* data = new RooDataSet("data", "data",RooArgSet(x));

// fit variable
Float_t jpsimass,jpsif;

// Read data file
TFile* input=new TFile("jpsi.root");
TTree* t1 = (TTree*) input->Get("h1");

// no of entries in the datafile

Int_t n_tot = (int)t1->GetEntries();
cout << " n_tot = " << n_tot << endl;
t1->SetBranchAddress("jpsimass",&jpsimass);
t1->SetBranchAddress("jpsif",&jpsif);

// Import the data points
  for(int i=0; i<n_tot; i++) {
      t1->GetEntry(i); 
  if(jpsif ==1){
  if(jpsimass >=2.9 && jpsimass <=3.3) {   
     x.setVal(jpsimass); 
     data->add(RooArgSet(x));
            
     }   
    }                                                  
  }
 
//TFile *nf = new TFile("nn_jpsi.root", "RECREATE"); 
TH1F *h1 = (TH1F*)data->createHistogram("my hist",x);
double scale = 1/h1->Integral();
h1->Scale(scale);
h1->SetLineColor(kRed);
h1->SetLineWidth(3);
 //nf->Write();
// nf->Close();

TCanvas *c1 = new TCanvas("c1","c1");
c1->cd();
h1->Draw();

}