Logo ROOT   6.21/01
Reference Guide
copytree2.C File Reference

Detailed Description

View in nbviewer Open in SWAN Copy a subset of a Tree to a new Tree, one branch in a separate file.

One branch of the new Tree is written to a separate file The input file has been generated by the program in $ROOTSYS/test/Event with the command Event 1000 1 1 1

// Load the library at macro parsing time: we need this to use its content in the code
R__LOAD_LIBRARY($ROOTSYS/test/libEvent.so)
void copytree2()
{
TString dir = "$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);
// 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 header. Do not copy events
TFile newfile("small.root", "recreate");
auto newtree = oldtree->CloneTree(0);
// Divert branch fH to a separate file and copy all events
newtree->GetBranch("fH")->SetFile("small_fH.root");
newtree->CopyEntries(oldtree);
newtree->Print();
newfile.Write();
}
Author
Rene Brun

Definition in file copytree2.C.