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Reference Guide
copytree3.C File Reference

Detailed Description

View in nbviewer Open in SWAN Example of Root macro to copy a subset of a Tree to a new Tree, selecting entries.

Only selected entries are copied to the new Tree. The input file has been generated by the program in $ROOTSYS/test/Event with Event 1000 1 99 1

R__LOAD_LIBRARY($ROOTSYS/test/libEvent.so)
void copytree3()
{
// Get old file, old tree and set top branch address
TString dir = "$ROOTSYS/test/Event.root";
const auto filename = gSystem->AccessPathName(dir) ? "./Event.root" : "$ROOTSYS/test/Event.root";
TFile oldfile(filename);
TTree *oldtree;
oldfile.GetObject("T", oldtree);
const auto nentries = oldtree->GetEntries();
Event *event = nullptr;
oldtree->SetBranchAddress("event", &event);
// Create a new file + a clone of old tree in new file
TFile newfile("small.root", "recreate");
auto newtree = oldtree->CloneTree(0);
for (auto i : ROOT::TSeqI(nentries)) {
oldtree->GetEntry(i);
if (event->GetNtrack() > 605)
newtree->Fill();
event->Clear();
}
newtree->Print();
newfile.Write();
}
Author
Rene Brun

Definition in file copytree3.C.