source: huonglan/ANA2011/SubtractTHF.C

void SubtractTHF()
{
  TFile *file1 = TFile::Open("res.root");
  
  TH1F *h1 = (TH1F*)file1->Get("mjjBest");
  TH1F *h2 = (TH1F*)file1->Get("mjjBest4leadingjets");

  TH1F *h = new TH1F("h", "", 100, 30, 130);

  int nentries = h1->GetNbinsX();

  cout << "nentries = " << nentries << endl;

  for (int i = 0; i < nentries; i++){
    int en1 = h1->GetBinContent(i);
    int en2 = h2->GetBinContent(i);

    int en = en1 - en2;
    
    h->SetBinContent(i,en);
  }

  h->Draw();

}