void compare()
{
  const int NFILES = 2;
  const char *infile[] = { "eff_files/muid_hvgroup_eff_MinJung.dat",
			   "eff_files/muid_hvgroup_eff_MuidSurvey.dat" };

  float eff, eff_err;
  int id;  
  int nagleplane;
  int iarm, iplane, ipanel, iorient, ihvg, roads_hit, roads_tot;
  
  const int MAXHVGROUPS = 360;
  float store_eff[NFILES][MAXHVGROUPS] = {{0}};
  float store_eff_err[NFILES][MAXHVGROUPS] = {{0}};

  for (int ifile=0; ifile<NFILES; ifile++) {
    for (ihvg=0; ihvg<MAXHVGROUPS; ihvg++) {
      store_eff[ifile][ihvg] = 0;
      store_eff_err[ifile][ihvg] = 0;
    }

    ifstream myfile;
    myfile.open(infile[ifile]);
    
    while (myfile.good()) {
      myfile >> iarm >> nagleplane >> ipanel >> ihvg >> roads_hit >> roads_tot >> eff;
      if (!myfile.good()) break;
      if (roads_tot == 0) {
      } // do nothing
      else {
	iplane = nagleplane/2;
	iorient = nagleplane%2;
	eff_err = sqrt(eff*(1-eff)/roads_tot);
	id = iarm*180 + nagleplane*18 + ipanel*3 + ihvg; 
	
	eff *= 100;
	eff_err *= 100;

	cout << " id " << id
	     << " eff " << eff
	     << " eff_err " << eff_err
	     << endl;
	store_eff[ifile][id] = eff;
	store_eff_err[ifile][id] = eff_err;
      }
    }
    myfile.close();
  }

  const float maximum_err = 0.05*100;
  float min = 0;
  float max = 120;
  int nbins = 120;

  int nbin_diff = 50;
  float min_diff = -5; 
  float max_diff = 5;

  TH2F *corr_all = new TH2F("corr_all","Asymm = MuidSurvey_eff - MinJung_eff vs MuidSurvey_eff : All",
			    nbins, min, max,
			    nbin_diff, min_diff, max_diff);
  TH2F *corr = new TH2F("corr","Asymm = MuidSurvey_eff - MinJung_eff vs MuidSurvey_eff ",
			nbins, min, max,
			nbin_diff, min_diff, max_diff);
  
  TH1F *h1corr = new TH1F("h1corr","Asymm = MuidSurvey_eff - MinJung_eff",
			  nbin_diff, min_diff, max_diff);
  TH1F *h1corr_all = new TH1F("h1corr_all","Asymm = MuidSurvey_eff - MinJung_eff : All",
			      nbin_diff, min_diff, max_diff);
  
  //creating histograms for plane by plane plot
  //===========================================
  
  TH1F *h1eff1[2][5];
  TH1F *h1eff2[2][5];
  TH1F *h1subs[2][5];
  TH1F *h1tot[2];
  char hname[100];
  
  for (int mm=0; mm<2; mm++){ // arm
    for (int nn=0; nn<5; nn++){ // gap
      sprintf(hname,"effi_1%d%d",mm,nn);
      h1eff1[mm][nn] = new TH1F(hname,hname, nbins, min, max);
      sprintf(hname,"effi_2%d%d",mm,nn);
      h1eff2[mm][nn] = new TH1F(hname,hname, nbins, min, max);
      sprintf(hname,"arm%d_gap%d",mm,nn);
      h1subs[mm][nn] = new TH1F(hname,hname,nbin_diff, min_diff, max_diff);
    }
    sprintf(hname,"arm%d_allgaps",mm);
    h1tot[mm] = new TH1F(hname,hname,nbin_diff, min_diff, max_diff);
  }

  // fill histograms
  //===========================================
  int armid, planeid, gapid;
  for (ihvg=0; ihvg<MAXHVGROUPS; ihvg++) {

    corr_all->Fill(store_eff[1][ihvg], store_eff[1][ihvg] - store_eff[0][ihvg]);
    h1corr_all->Fill(store_eff[1][ihvg] - store_eff[0][ihvg]);
    
    if ( store_eff_err[0][ihvg] < maximum_err && store_eff_err[0][ihvg]>0 ) { 
      corr->Fill(store_eff[1][ihvg], store_eff[1][ihvg] - store_eff[0][ihvg]);
      h1corr->Fill(store_eff[1][ihvg] - store_eff[0][ihvg]);
      
      armid = ihvg/180;
      planeid = (ihvg%180)/18;
      gapid = planeid/2;
      h1eff1[armid][gapid]->Fill(store_eff[1][ihvg]);
      h1eff2[armid][gapid]->Fill(store_eff[0][ihvg]);
      h1subs[armid][gapid]->Fill(store_eff[1][ihvg] - store_eff[0][ihvg]);
      
      h1tot[armid]->Fill(store_eff[1][ihvg] - store_eff[0][ihvg]);
    }
  }
  
  TCanvas *cSouth = new TCanvas("cSouth","cSouth",10,10,800,600);
  cSouth->Divide(3,2);
  TCanvas *cNorth = new TCanvas("cNorth","cNorth",10,10,800,600);
  cNorth->Divide(3,2);
  
  gStyle->SetOptStat(1001110);
  gStyle->SetStatH(0.22);
  gStyle->SetStatW(0.40);
  
  for (int m=0; m<2; m++){
    for (int n=0; n<5; n++){
      if(m==0) cSouth->cd(n+1);
      if(m==1) cNorth->cd(n+1);
      h1subs[m][n]->SetLabelSize(0.05,"X");
      h1subs[m][n]->SetLabelSize(0.05,"Y");
      h1subs[m][n]->SetXTitle("(MuidSurvey_eff) - (MinJung/DB_eff)");
      h1subs[m][n]->SetTitleSize(0.05,"X");
      h1subs[m][n]->Draw();
    }
    if(m==0) {
      cSouth->cd(6);
      h1tot[0]->SetXTitle("(MuidSurvey_eff) - (MinJung/DB_eff)");
      h1tot[0]->SetTitleSize(0.05,"X");
      h1tot[0]->Draw();
    }else if(m==1){
      cNorth->cd(6);
      h1tot[1]->Draw();
      h1tot[1]->SetXTitle("(MuidSurvey_eff) - (MinJung/DB_eff)");
      h1tot[1]->SetTitleSize(0.05,"X");
    }
  }
  
  cSouth->SaveAs("compare_south.gif");
  cNorth->SaveAs("compare_north.gif");

}