Copytree 3

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

Author: Rene Brun
This notebook tutorial was automatically generated with ROOTBOOK-izer (Beta) from the macro found in the ROOT repository on Tuesday, January 17, 2017 at 02:42 PM.



In [1]:

    
.! $ROOTSYS/test/eventexe 1000 1 1 1









    









    



sh: /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.08.02-99084/x86_64-slc6-gcc49-opt/test/eventexe: No such file or directory



In [2]:

    
gSystem->Load("$ROOTSYS/test/libEvent");









    



Error in <TUnixSystem::FindDynamicLibrary>: $ROOTSYS/test/libEvent[.so | .dll | .dylib | .sl | .dl | .a] does not exist in /cvmfs/sft.cern.ch/lcg/views/LCG_87/x86_64-slc6-gcc49-opt/lib64:/cvmfs/sft.cern.ch/lcg/views/LCG_87/x86_64-slc6-gcc49-opt/lib:/cvmfs/sft.cern.ch/lcg/contrib/gcc/4.9/x86_64-slc6/lib64:.:/cvmfs/sft.cern.ch/lcg/releases/ROOT/6.08.02-99084/x86_64-slc6-gcc49-opt/lib:/lib64/tls/x86_64:/lib64/tls:/lib64/x86_64:/lib64:/usr/lib64/tls/x86_64:/usr/lib64/tls:/usr/lib64/x86_64:/usr/lib64

Get old file, old tree and set top branch address



In [3]:

    
TFile *oldfile;
TString dir = "$ROOTSYS/test/Event.root";
gSystem->ExpandPathName(dir);
if (!gSystem->AccessPathName(dir))
    {oldfile = new TFile("$ROOTSYS/test/Event.root");}
else {oldfile = new TFile("./Event.root");}
TTree *oldtree = (TTree*)oldfile->Get("T");
Long64_t nentries = oldtree->GetEntries();
Event *event   = 0;
oldtree->SetBranchAddress("event",&event);









    



Error in <TFile::TFile>: file ./Event.root does not exist
    __boot()
    import os
Error in <HandleInterpreterException>: Trying to dereference null pointer or trying to call routine taking non-null arguments.
Execution of your code was aborted.
input_line_29:9:21: warning: null passed to a callee that requires a non-null argument [-Wnonnull]
Long64_t nentries = oldtree->GetEntries();
                    ^~~~~~~

Create a new file + a clone of old tree in new file



In [4]:

    
TFile *newfile = new TFile("small.root","recreate");
TTree *newtree = oldtree->CloneTree(0);

for (Long64_t i=0;i<nentries; i++) {
   oldtree->GetEntry(i);
   if (event->GetNtrack() > 605) newtree->Fill();
   event->Clear();
}
newtree->Print();
newtree->AutoSave();
delete oldfile;
delete newfile;









    



input_line_32:7:8: error: use of undeclared identifier 'event'
   if (event->GetNtrack() > 605) newtree->Fill();
       ^
input_line_32:8:4: error: use of undeclared identifier 'event'
   event->Clear();
   ^