overlay.C

void overlay(TString hist1name, TString hist2name, Bool_t golden=false,TString samestr=""){
  TH1F* H1;
  TH1F* H2;
  
  H1 = (TH1F*) gDirectory->Get(hist1name);
  H2 = (TH1F*) gDirectory->Get(hist2name);
  if (H1 && H2) {
  if(golden){
    H1->SetLineColor(30);
    H1->SetFillColor(30);
    H1->SetFillStyle(3027);
    H2->SetLineColor(46);
    H2->SetFillColor(46);
    H2->SetFillStyle(3027);
  } else {
    H1->SetLineColor(4);
    H2->SetLineColor(2);
    H1->SetStats(0);
    H2->SetStats(0);
    H1->SetMinimum(0);
    H2->SetMinimum(0);
  }

  if(golden){
    if(!samestr.Contains("sames")) samestr += "sames";
    H1->Draw(samestr);
    H2->Draw(samestr);
  } else {
    if(!golden && !samestr.Contains("sames")){
      // pick which hist to draw first:
      if(H1->GetMaximum() > H2->GetMaximum()){
	H1->Draw(samestr);
	if(!samestr.Contains("sames")) samestr += "sames";
	H2->Draw(samestr);
      } else {
	H2->Draw(samestr);
	if(!samestr.Contains("sames")) samestr += "sames";
	H1->Draw(samestr);
      }
    } else {
      H1->Draw(samestr);
      if(!samestr.Contains("sames")) samestr += "sames";
      H2->Draw(samestr);
    H2->GetXaxis()->SetTitleOffset(.6);
    H2->GetXaxis()->SetTitleSize(0.08);
    H2->GetYaxis()->SetTitleOffset(.6);
    H2->GetYaxis()->SetTitleSize(0.08);
    }
  }
  } else {
    if (!H1) cout << " Histogram " << hist1name << " does not exist" << endl;
    if (!H2) cout << " Histogram " << hist2name << " does not exist" << endl;
  }
}