/**
 g++ $(root-config --cflags) $(root-config --libs) -o tefficiency.exe tefficiency.cc
 */
#include "TH1.h"
#include "TGraphAsymmErrors.h"
#include "TList.h"
#include "TEfficiency.h"

void tefficiency() {
  Double_t a_num=1000., a_den=2000.;
  Double_t b_num=100.,  b_den=200.;
  Double_t d_num=900.,  d_den=1000.;
  
  TEfficiency *effa = new TEfficiency("effa", "effa", 1, 0., 1.);
  TEfficiency *effb = new TEfficiency("effb", "effb", 1, 0., 1.);
  TEfficiency *effd = new TEfficiency("effd", "effd", 1, 0., 1.);
  
  effa->SetTotalEvents(1, a_den);  effa->SetPassedEvents(1, a_num);
  effb->SetTotalEvents(1, b_den);  effb->SetPassedEvents(1, b_num);
  effd->SetTotalEvents(1, d_den);  effd->SetPassedEvents(1, d_num);
  
  
  TList *pList = new TList();
  Double_t weights1[2] = {1., 1.} ;
  
  TGraphAsymmErrors *tg = NULL;
  Double_t x, y;

  pList->Add(effa);
  pList->Add(effd);
  tg = TEfficiency::Combine(pList, "", 2, weights1);
  tg->GetPoint(0,x,y);
  printf("effa (%f)  (+)  effd (%f) : %f\n", weights1[0], weights1[1], y);
  pList->Clear();
  
  pList->Add(effb);
  pList->Add(effd);
  tg = TEfficiency::Combine(pList, "", 2, weights1);
  tg->GetPoint(0,x,y);
  printf("effb (%f)  (+)  effd (%f) : %f\n", weights1[0], weights1[1], y);
  pList->Clear();
  
// Reweight with total events
  weights1[0] = 1. * ((Double_t) effa->GetTotalHistogram()->GetBinContent(1))
    / ((Double_t) effb->GetTotalHistogram()->GetBinContent(1)) ;
  pList->Add(effb);
  pList->Add(effd);
  tg = TEfficiency::Combine(pList, "", 2, weights1);
  tg->GetPoint(0,x,y);
  printf("effb (%f)  (+)  effd (%f) : %f (reweighted)\n", weights1[0], weights1[1], y);
  pList->Clear();
}


int main(int argc, const char* argv[]) {
  tefficiency();
  return 0;
}