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copytree3.C
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1/// \file
2/// \ingroup tutorial_tree
3/// \notebook -nodraw
4/// Example of Root macro to copy a subset of a Tree to a new Tree, selecting entries.
5///
6/// Only selected entries are copied to the new Tree.
7/// The input file has been generated by the program in `$ROOTSYS/test/Event`
8/// with `Event 1000 1 99 1`
9///
10/// \macro_code
11///
12/// \author Rene Brun
13
14R__LOAD_LIBRARY($ROOTSYS/test/libEvent.so)
15
16void copytree3()
17{
18 // Get old file, old tree and set top branch address
19 TString dir = "$ROOTSYS/test/Event.root";
21 const auto filename = gSystem->AccessPathName(dir) ? "./Event.root" : "$ROOTSYS/test/Event.root";
22
23 TFile oldfile(filename);
24 TTree *oldtree;
25 oldfile.GetObject("T", oldtree);
26
27 const auto nentries = oldtree->GetEntries();
28
29 Event *event = nullptr;
30 oldtree->SetBranchAddress("event", &event);
31
32 // Create a new file + a clone of old tree in new file
33 TFile newfile("small.root", "recreate");
34 auto newtree = oldtree->CloneTree(0);
35
36 for (auto i : ROOT::TSeqI(nentries)) {
37 oldtree->GetEntry(i);
38 if (event->GetNtrack() > 605)
39 newtree->Fill();
40 event->Clear();
41 }
42
43 newtree->Print();
44 newfile.Write();
45}
#define R__LOAD_LIBRARY(LIBRARY)
Definition: Rtypes.h:489
Option_t Option_t TPoint TPoint const char GetTextMagnitude GetFillStyle GetLineColor GetLineWidth GetMarkerStyle GetTextAlign GetTextColor GetTextSize void char Point_t Rectangle_t WindowAttributes_t Float_t Float_t Float_t Int_t Int_t UInt_t UInt_t Rectangle_t Int_t Int_t Window_t TString Int_t GCValues_t GetPrimarySelectionOwner GetDisplay GetScreen GetColormap GetNativeEvent const char const char dpyName wid window const char font_name cursor keysym reg const char only_if_exist regb h Point_t winding char text const char depth char const char Int_t count const char ColorStruct_t color const char filename
int nentries
Definition: THbookFile.cxx:91
R__EXTERN TSystem * gSystem
Definition: TSystem.h:559
A pseudo container class which is a generator of indices.
Definition: TSeq.hxx:67
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:1274
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:1296
A TTree represents a columnar dataset.
Definition: TTree.h:79
virtual Int_t GetEntry(Long64_t entry, Int_t getall=0)
Read all branches of entry and return total number of bytes read.
Definition: TTree.cxx:5612
virtual Int_t SetBranchAddress(const char *bname, void *add, TBranch **ptr=0)
Change branch address, dealing with clone trees properly.
Definition: TTree.cxx:8354
virtual Long64_t GetEntries() const
Definition: TTree.h:459
virtual TTree * CloneTree(Long64_t nentries=-1, Option_t *option="")
Create a clone of this tree and copy nentries.
Definition: TTree.cxx:3110
void(off) SmallVectorTemplateBase< T
Definition: test.py:1