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copytree2.C
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1/// \file
2/// \ingroup tutorial_tree
3/// \notebook -nodraw
4/// Copy a subset of a Tree to a new Tree, one branch in a separate file.
5///
6/// One branch of the new Tree is written to a separate file
7/// The input file has been generated by the program in `$ROOTSYS/test/Event`
8/// with the command `Event 1000 1 1 1`
9///
10/// \macro_code
11///
12/// \author Rene Brun
13
14// Load the library at macro parsing time: we need this to use its content in the code
15R__LOAD_LIBRARY($ROOTSYS/test/libEvent.so)
16
17void copytree2()
18{
19
20 TString dir = "$ROOTSYS/test/Event.root";
22 const auto filename = gSystem->AccessPathName(dir) ? "./Event.root" : "$ROOTSYS/test/Event.root";
23
24 TFile oldfile(filename);
25 TTree *oldtree;
26 oldfile.GetObject("T", oldtree);
27
28 // Activate only four of them
29 for (auto activeBranchName : {"event", "fNtrack", "fNseg", "fH"}) {
30 oldtree->SetBranchStatus(activeBranchName, 1);
31 }
32
33 // Create a new file + a clone of old tree header. Do not copy events
34 TFile newfile("small.root", "recreate");
35 auto newtree = oldtree->CloneTree(0);
36
37 // Divert branch fH to a separate file and copy all events
38 newtree->GetBranch("fH")->SetFile("small_fH.root");
39 newtree->CopyEntries(oldtree);
40
41 newtree->Print();
42 newfile.Write();
43}
#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
R__EXTERN TSystem * gSystem
Definition: TSystem.h:559
virtual void SetFile(TFile *file=nullptr)
Set file where this branch writes/reads its buffers.
Definition: TBranch.cxx:2780
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 TBranch * GetBranch(const char *name)
Return pointer to the branch with the given name in this tree or its friends.
Definition: TTree.cxx:5256
virtual TTree * CloneTree(Long64_t nentries=-1, Option_t *option="")
Create a clone of this tree and copy nentries.
Definition: TTree.cxx:3110
virtual void SetBranchStatus(const char *bname, Bool_t status=1, UInt_t *found=0)
Set branch status to Process or DoNotProcess.
Definition: TTree.cxx:8491
void(off) SmallVectorTemplateBase< T
Definition: test.py:1