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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

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)) {
if (event->GetNtrack() > 605)
Definition Rtypes.h:472
int nentries
R__EXTERN TSystem * gSystem
Definition TSystem.h:559
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition TFile.h:54
Basic string class.
Definition TString.h:136
virtual Bool_t ExpandPathName(TString &path)
Expand a pathname getting rid of special shell characters like ~.
Definition TSystem.cxx:1272
virtual Bool_t AccessPathName(const char *path, EAccessMode mode=kFileExists)
Returns FALSE if one can access a file using the specified access mode.
Definition TSystem.cxx:1294
A TTree represents a columnar dataset.
Definition TTree.h:79
virtual Int_t SetBranchAddress(const char *bname, void *add, TBranch **ptr=0)
Change branch address, dealing with clone trees properly.
Definition TTree.cxx:8349
virtual Long64_t GetEntries() const
Definition TTree.h:460
virtual TTree * CloneTree(Long64_t nentries=-1, Option_t *option="")
Create a clone of this tree and copy nentries.
Definition TTree.cxx:3124
virtual Int_t GetEntry(Long64_t entry=0, Int_t getall=0)
Read all branches of entry and return total number of bytes read.
Definition TTree.cxx:5618
tbb::task_arena is an alias of tbb::interface7::task_arena, which doesn't allow to forward declare tb...
Definition test.py:1
Rene Brun

Definition in file copytree3.C.