swh:1:snp:af87cd67498ef4fe47c76ed3e7caffe5b61facaf
Tip revision: 82fc2dc7e13477e717020c761e227ed4e3f7012e authored by Axel Naumann on 07 June 2022, 15:59:39 UTC
"Update ROOT version files to v6.26/04."
"Update ROOT version files to v6.26/04."
Tip revision: 82fc2dc
copytree2.C
/// \file
/// \ingroup tutorial_tree
/// \notebook -nodraw
/// 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 `$ROOTSYS/test/Event`
/// with the command `Event 1000 1 1 1`
///
/// \macro_code
///
/// \author Rene Brun
// Load the library at macro parsing time: we need this to use its content in the code
R__LOAD_LIBRARY($ROOTSYS/test/libEvent.so)
void copytree2()
{
TString dir = "$ROOTSYS/test/Event.root";
gSystem->ExpandPathName(dir);
const auto filename = gSystem->AccessPathName(dir) ? "./Event.root" : "$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();
}