#include <iostream>
#include <TFile.h>
#include <TChain.h>
#include <TTree.h>
#include <TFormula.h>
#include <TTreeFormula.h>

void make_subsample2(void)
{
TChain *fChain = new TChain("tsm");
fChain->Add("/work/eowyn-clued0/noeding/ROOT/zee60_130/data/diem/0/D0ChunkAnalyze.root");
fChain->Add("/work/eowyn-clued0/noeding/ROOT/zee60_130/data/diem/1/D0ChunkAnalyze.root");
fChain->Add("/work/eowyn-clued0/noeding/ROOT/zee60_130/data/diem/2/D0ChunkAnalyze.root");
fChain->Add("/work/eowyn-clued0/noeding/ROOT/zee60_130/data/diem/3/D0ChunkAnalyze.root");
fChain->Add("/work/eowyn-clued0/noeding/ROOT/zee60_130/data/diem/4/D0ChunkAnalyze.root");

TFile *newfile = new TFile("zee60_130_subsample.root","recreate");
TTree* newtree = get_new_tree(fChain);
//(TTree*)fChain->CopyTree("LETM_Nelectron>1");
newfile->Write();
newfile->Close();
}

TTree get_new_tree(TChain *ch) {

  TTree *tree = ch->CloneTree(0);
  TTree *fTree = ch->CloneTree(0);
  if (tree == 0) return 0;

  Int_t firstentry=0;
  Int_t nentries=fTree->GetEntriesFast();

  Int_t entry,entryNumber;
  Int_t lastentry = firstentry + nentries -1;
   if (lastentry > fTree->GetEntriesFast()-1) {
      lastentry  = (Int_t)fTree->GetEntriesFast() -1;
      nentries   = lastentry - firstentry + 1;
   }

   // Compile selection expression if there is one
   TTreeFormula *select = 0; // no need to interfer with fSelect since we
                             // handle the loop explicitly below and can call
                             // UpdateFormulaLeaves ourselves.
   select = new TTreeFormula("Selection","LETM_Nelectron>1",fTree);
 
    //if (strlen(selection)) {
   // select = new TTreeFormula("Selection",selection,fTree);
   // if (!select || !select->GetNdim()) { delete select; }
   // fFormulaList->Add(select);
   //}

   //loop on the specified entries
   Int_t tnumber = -1;
   for (entry=firstentry;entry<firstentry+nentries;entry++) {
      entryNumber = fTree->GetEntryNumber(entry);
      if (entryNumber < 0) break;
      Int_t localEntry = fTree->LoadTree(entryNumber);
      if (localEntry < 0) break;
      if (tnumber != fTree->GetTreeNumber()) {
         tnumber = fTree->GetTreeNumber();
         if (select) select->UpdateFormulaLeaves();
      }
      if (select) {
         Int_t ndata = select->GetNdata();
         Bool_t keep = kFALSE;
         for(Int_t current = 0; current<ndata && !keep; current++) {
            keep |= (select->EvalInstance(current) != 0);
         }
         if (!keep) continue;
      }
      fTree->GetEntry(entryNumber);
      tree->Fill();
   }
   fFormulaList->Clear();
   return tree;

}