ROOT_528-00b_version: tutorials/tree/copytree2.C Source File

00001 void copytree2() {
00002 // Example of Root macro to copy a subset of a Tree to a new Tree
00003 // One branch of the new Tree is written to a separate file
00004 // The input file has been generated by the program in $ROOTSYS/test/Event
00005 // with   Event 1000 1 1 1
00006 //Author: Rene Brun
00007    
00008    gSystem->Load("$ROOTSYS/test/libEvent");
00009 
00010    //Get old file, old tree and set top branch address
00011    TFile *oldfile = new TFile("$ROOTSYS/test/Event.root");
00012    TTree *oldtree = (TTree*)oldfile->Get("T");
00013    Event *event   = new Event();
00014    oldtree->SetBranchAddress("event",&event);
00015    oldtree->SetBranchStatus("*",0);
00016    oldtree->SetBranchStatus("event",1);
00017    oldtree->SetBranchStatus("fNtrack",1);
00018    oldtree->SetBranchStatus("fNseg",1);
00019    oldtree->SetBranchStatus("fH",1);
00020 
00021 
00022    //Create a new file + a clone of old tree header. Do not copy events
00023    TFile *newfile = new TFile("small.root","recreate");
00024    TTree *newtree = oldtree->CloneTree(0);
00025 
00026    //Divert branch fH to a separate file and copy all events
00027    newtree->GetBranch("fH")->SetFile("small_fH.root");
00028    newtree->CopyEntries(oldtree);
00029 
00030    newtree->Print();
00031    newfile->Write();
00032    delete oldfile;
00033    delete newfile;
00034 }