TFile *f2 = new TFile("rffc_Good_dataQA.root");
TH1F *h1 = (TH1F*)f2->Get("hgdca_protonN0");
TH1F *h2 = (TH1F*)f2->Get("hgdca_protonP0");


void fit_sample()
{
  Double_t ftotal(Double_t *x, Double_t *par);  
  
  gStyle->SetOptFit(1);
    
  TCanvas *c1 = new TCanvas("c1","",600,600);
  h2->Draw();
  
  c1->SetLogy();
  
  TF1 *func = new TF1("func",ftotal,0,15, 4);
  func->SetLineColor(2);
  func->SetParameters(0.95, 0.70, 1.076, 5.66);
  func->SetParNames("r", "A", "B", "C"); 
  //  h2->Fit("func", "V+");       
  h2->Fit("func", "R");       
  
  // ----- Getting Integral for the ftotal fn ----- //
  
  cout<<"Integral of a ftotal fn. ===== " <<func->Integral(0,15)<<endl;
  cout<<"With DCA cut -- Integral of a ftotal fn. ===== " <<func->Integral(0,3)<<endl;
  
}


Double_t ftotal(Double_t *x, Double_t *par) {
  Double_t xx = x[0];
  //  Int_t bin = h1->GetXaxis()->FindBin(x[0]);
  Int_t bin = h1->GetXaxis()->FindBin(xx);
  //  cout <<"xx = "<<xx<<"  " << "bin = " <<bin<<endl;
  Float_t br = h1->GetBinContent(bin);
  
  if(par[0]!= 0)  Double_t br1= br/par[0];
  if(par[2] != 0) Double_t bk = par[1]*TMath::Power((1-TMath::Exp(-(x[0])/par[2])),par[3]);
  Double_t tot = br1 + bk;
  return  tot;
  cout <<"xx = "<<xx<<"  "<<"bin = "<<bin<<"" << "bin content = " <<br<<endl;
  cout<<"Value of total fn is : "<<tot<<endl;
}