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copytree2.C File Reference

Detailed Description

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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

// 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";
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();
}
#define R__LOAD_LIBRARY(LIBRARY)
Definition Rtypes.h:496
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:561
virtual void SetFile(TFile *file=nullptr)
Set file where this branch writes/reads its buffers.
Definition TBranch.cxx:2863
A ROOT file is an on-disk file, usually with extension .root, that stores objects in a file-system-li...
Definition TFile.h:53
Basic string class.
Definition TString.h:139
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 void SetBranchStatus(const char *bname, bool status=true, UInt_t *found=nullptr)
Set branch status to Process or DoNotProcess.
Definition TTree.cxx:8534
virtual TBranch * GetBranch(const char *name)
Return pointer to the branch with the given name in this tree or its friends.
Definition TTree.cxx:5294
virtual TTree * CloneTree(Long64_t nentries=-1, Option_t *option="")
Create a clone of this tree and copy nentries.
Definition TTree.cxx:3139
Author
Rene Brun

Definition in file copytree2.C.