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Reference Guide
copytree.C File Reference

Detailed Description

View in nbviewer Open in SWAN Copy a subset of a Tree to a new Tree

The input file has been generated by the program in $ROOTSYS/test/Event with Event 1000 1 1 1.

// Load the library at macro parsing time: we need this to use its content in the code
void copytree()
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);
// Deactivate all branches
oldtree->SetBranchStatus("*", 0);
// Activate only four of them
for (auto activeBranchName : {"event", "fNtrack", "fNseg", "fH"})
oldtree->SetBranchStatus(activeBranchName, 1);
// Create a new file + a clone of old tree in new file
TFile newfile("small.root", "recreate");
auto newtree = oldtree->CloneTree();
Rene Brun

Definition in file copytree.C.