[ROOT] Filling TTrees From Existing Trees

From: John H Loizides (jhl@hep.ucl.ac.uk)
Date: Wed Mar 07 2001 - 18:08:27 MET 

Can Someone help me please I am trying to create a new root file from an
existing root file with some cuts imposed on the TTree. My code is below
with no cuts so it sould create the same root file. But does not seem to
fill the TTree with anything.

main()
{


TFile *f =
(TFile*)gROOT->GetListOfFiles()->FindObject("97NCBACKq400.root");
   if (!f) {
      f = new TFile("97NCBACKq400.root");
   }
   TTree *h1 = (TTree*)gDirectory->Get("h1");


   Float_t         Cal_e;
   Float_t         Cal_et;
   Float_t         Cal_empz;
   Float_t         Cal_pt;

   Float_t         aCal_e;
   Float_t         aCal_et;
   Float_t         aCal_empz;
   Float_t         aCal_pt;



   h1->SetBranchAddress("Cal_e",&Cal_e);
   h1->SetBranchAddress("Cal_et",&Cal_et);
   h1->SetBranchAddress("Cal_empz",&Cal_empz);
   h1->SetBranchAddress("Cal_pt",&Cal_pt);

   TFile *outfile = new TFile("S3.root","RECREATE");   

   TTree *h11 = new TTree("T","A new Tree"); 

   h11->Branch("Cal_e",&aCal_e);
   h11->Branch("Cal_et",&aCal_et);
   h11->Branch("Cal_empz",&aCal_empz);
   h11->Branch("Cal_pt",&aCal_pt);
   Int_t nentries = h1->GetEntries();

for (Int_t i=0; i<nentries;i++) 
{
  h1->GetEntry(i);
 
  h11->Fill();

}//for i
 
h11->Write();
outfile->Write();

outfile->Close();



}//main



Thanks 


John Loizides

4th Year Student UCL Physics

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