//---------------------------------------------------------------------------
//
// This root macro file is used for readinf ntuple file named output.root.
//
// Mar 2024
//---------------------------------------------------------------------------
void ntupleReader(){
  // input file and its tree
  TFile *input = new TFile("output.root","read");
  TTree *tree  = (TTree*) input->Get("Values");

  // my local variables
  int evt, pdgid;
  double px,py,pz,pmag;

  // sent branch adr.
  tree->SetBranchAddress("Event",   &evt);
  tree->SetBranchAddress("PDGcode", &pdgid);
  tree->SetBranchAddress("pmag",    &pmag);
  tree->SetBranchAddress("px",      &px);
  tree->SetBranchAddress("py",      &py);
  tree->SetBranchAddress("pz",      &pz);

  // total number of entreis
  int entries = tree->GetEntries();
  cout << "Total # of entries = " << entries << endl;

  cout << "I will print first 10 of the data\n";
  for(int i=0; i<10; i++){
    tree->GetEntry(i);
    cout << evt << " " << pdgid << " " << pmag << endl;
  }

  // --- analysis starts from here ---
  TCanvas *c1 = new TCanvas();
  TH1F *h1 = new TH1F("hMomentum",";momentum (MeV);Entries",100,900,1000);
  TH2F *h2 = new TH2F("hpxpy",";px (MeV);py (MeV)",100,-150,150, 100,-150,150);

  cout << "I will analyse all data\n";
  for(int i=0; i<entries; i++){
    tree->GetEntry(i);
    h1->Fill(pmag);
    h2->Fill(px, py);
  }

  c1->Divide(2,1);
  c1->cd(1); h1->Draw();
  c1->cd(2); h2->Draw();
}