void plot2(const char *armname = "North") {

  /*
  const int nfiles = 6;
  const char *fileId[] = { "Melynda", "Catherine", "MinJung", "None", "MuidSurvey", "MuidSurvey2" };
  const int color[nfiles] = { 1,5,4,6,8,2};
  const int style[nfiles] = { 8,4, 29,30, 21,25 };
  */
  const int nfiles = 5;
  const char *fileId[] = { "Melynda", "Catherine", "MuidSurvey", "MuidSurvey2", "VC" };
  const int color[nfiles] = { 1,5,4,8,2};
  const int style[nfiles] = { 8,4, 29, 21,25 };

  /*
  const int nfiles = 3;
  const char *fileId[] = { "Melynda", "MuidSurvey", "MuidSurvey2" };
  const int color[nfiles] = { 1,8,2};
  const int style[nfiles] = { 8,21,25 };
  */
  int nbins = 30;
  float low = 150;
  float high = 450;

  TH1F *dg0_r[nfiles];
  char id[100];
  for (int ifile=0; ifile<nfiles; ifile++) {
    sprintf(id,"dg0_r[%d]",ifile);
    dg0_r[ifile] = new TH1F(id,"sqrt(Tr0_DG0x**2+Tr0_DG0y**2) vs Radius (for p=3-7 GeV/c)",nbins,low,high);
  }

  char filename[200];
  TCut north_mut = "charge==0&&Tr0_chi2<30&&Tr1_chi2<30&&Evt_vtxchi2<4&&Tr0_DG0<15&&Tr1_DG0<15&&Tr0_DDG0<9&&Tr1_DDG0<9&&rapidity>1.2&&rapidity<2.2";

  char drawcmd[100];

  int maxid = -1;
  float max = -999;
  float min = 999;

  for (int ifile=0; ifile<nfiles; ifile++) {
    sprintf(filename,"/phenix/data08/silvermy/run5pp_alignment/%s_%s.root",armname,fileId[ifile]);
    TFile f(filename);
    cout << "filename " << filename << " entries " << dimuons->GetEntries() << endl;

    sprintf(id,"dg0%d",ifile);
    TProfile *dg0 = new TProfile(id,"sqrt(Tr0_DG0x**2+Tr0_DG0y**2) vs Momentum",nbins,low,high);
    sprintf(drawcmd,"sqrt(Tr0_DG0x**2+Tr0_DG0y**2):sqrt(muID_gap0_x0**2+muID_gap0_y0**2)>>%s",id);
    dg0->Reset();
    dimuons->Draw(drawcmd,north_mut&&"sqrt(Tr0_px**2+Tr0_py**2+Tr0_pz**2)>4&&sqrt(Tr0_px**2+Tr0_py**2+Tr0_pz**2)<7&&(muID_gap0_x0>110&&muID_gap0_y0>20)","prof");

    cout << " dg0 max " << dg0->GetMaximum() << endl;

    for (int ibin = 0; ibin<=dg0->GetNbinsX(); ibin++) {
      Stat_t cont = dg0->GetBinContent(ibin);
      Stat_t err = dg0->GetBinError(ibin);
      /*
      cout << " ibin " << ibin
	   << " cont " << cont
	   << " err " << err
	   << endl;
      */
      dg0_r[ifile]->SetBinContent(ibin, cont);
      dg0_r[ifile]->SetBinError(ibin, err);
      /*
      cont = dg0_r[ifile]->GetBinContent(ibin);
      err = dg0_r[ifile]->GetBinError(ibin);
      cout << " ibin " << ibin
	   << " dg0_r cont " << cont
	   << " dg0_r err " << err
	   << endl;
      */
    }

    cout << " dg0_r max " << dg0_r[ifile]->GetMaximum() << endl;

    dg0_r[ifile]->SetMarkerColor(color[ifile]);
    dg0_r[ifile]->SetMarkerStyle(style[ifile]);
    dg0_r[ifile]->SetMarkerSize(1.0);
    dg0_r[ifile]->SetLineColor(color[ifile]);

    if (dg0_r[ifile]->GetMaximum() > max) {
      max = dg0_r[ifile]->GetMaximum();
      maxid = ifile;
    }
    if (dg0_r[ifile]->GetMinimum() < min) {
      min = dg0_r[ifile]->GetMinimum();
    }

  }

  // plot the one with the maximum value first
  cout << " max " << max << " maxid " << maxid << endl;
  dg0_r[maxid]->GetYaxis()->SetTitle("sqrt(Tr0_DG0x**2+Tr0_DG0y**2)");
  dg0_r[maxid]->GetXaxis()->SetTitle("sqrt(muID_gap0_x0**2+muID_gap0_y0**2)");

  gStyle->SetOptStat(0);
  dg0_r[maxid]->SetMaximum(max*1.1);
  //  dg0_r[maxid]->SetMinimum(min*0.9);
  dg0_r[maxid]->SetMinimum(0);
  dg0_r[maxid]->Draw("p");

  // plot all on "same"; add to legend
  TLegend *leg = new TLegend(0.15,0.7,0.35,0.89);
  char text[100];
  for (int ifile=0; ifile<nfiles; ifile++) {
    cout << " ifile " << ifile << endl; 
    dg0_r[ifile]->Draw("p same");
    sprintf (text, "%s", fileId[ifile]);
    leg->AddEntry(dg0_r[ifile],text,"p");
  }
  leg->Draw();

  cout << " done " << endl;
  c1->Update();
  c1->SaveAs("plot2.gif");
}