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/*************************************************
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Given a root file containing a TTree, this
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macro will place half the contents into 2 new
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files.
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Can be run from a bash prompt as well:
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root -b -l -q "splitTreeInFile.C(\"PhotonJetPt15_Summer09.root\",\"TreePhotonJet\")"
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Or used within root:
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$ root -l
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root [0] .L splitTreeInFile.C
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root [1] splitTreeInFile("PhotonJetPt15_Summer09.root","TreePhotonJet")
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Opened PhotonJetPt15_Summer09.root...
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Copying TreePhotonJet to two new files...
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Created
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PhotonJetPt15_Summer09_1stHalf.root
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PhotonJetPt15_Summer09_2ndHalf.root
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done.
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root [2]
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Michael B. Anderson
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Oct 8, 2009
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*************************************************/
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void splitTreeInFile(TString origFilename, TString treeName) {
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// Create names for the two new files
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TString filenameString = origFilename;
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filenameString.ReplaceAll(".root","");
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TString newFilename1 = filenameString + "_1stHalf.root";
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TString newFilename2 = filenameString + "_2ndHalf.root";
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///////////////////////////////////////////////////////////
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//Get old file, old tree and set top branch address
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TFile *oldFile = new TFile(origFilename);
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if (oldFile->IsZombie()) {
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cout << "ERROR: " << origFilename << " not found" << endl;
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return;
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}
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cout << "Opened " << origFilename << "..." << endl;
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TTree *oldTree = (TTree*)oldFile->Get(treeName);
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if (!oldTree) {
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cout << "ERROR: " << treeName << " not found in " << origFilename << endl;
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return;
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}
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Int_t numOfEntries = (Int_t)oldTree->GetEntries();
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///////////////////////////////////////////////////////////
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//Create a new file + a clone of old tree in new file
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TFile *newFile1 = new TFile(newFilename1,"recreate");
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TTree *newTree1 = oldTree->CloneTree(0);
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TFile *newFile2 = new TFile(newFilename2,"recreate");
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TTree *newTree2 = oldTree->CloneTree(0);
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// Copy tree into new trees
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cout << "Copying " << treeName << " to two new files..." << endl;
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for (Int_t i=0;i<numOfEntries; i++) {
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oldTree->GetEntry(i);
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if (i<numOfEntries/2) {
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newTree1->Fill();
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} else {
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newTree2->Fill();
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}
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}
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newTree1->AutoSave();
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newTree2->AutoSave();
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newFile1->Close();
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newFile2->Close();
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cout << "Created\n " << newFilename1 << "\n " << newFilename2 << endl << "done." << endl;
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}
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