Showing two histograms on one canvas

ROOT
1

Hi Rooters
I am trying to show two histograms on one canvas on top of each other for comparison reasons. Here is the code:

#include "Riostream.h"
#include "TString.h"
#include "TMath.h"

void COMPARISON_SCRIPT()
{
        TFile *READ_File1 = new TFile("/Users/aibutt/BLACKHOLE_ANALYSIS/DATA2011/non-commutative/D1_STEPPED_ANALYSIS_2011.root", "READ");

        READ_File1 -> cd();
        TH1F *RD1 = (TH1F*)gDirectory -> Get("SumPT_CR_800_1200_EF_j240_a4tc_EFFS");
        TH1F *RD2 = (TH1F*)gDirectory -> Get("SumPT_SR_1200PLUS_EF_j240_a4tc_EFFS");

        gStyle -> SetOptStat(0000000);

        TCanvas *canvas_1 = new TCanvas("canvas_1", "canvas_1", 0,0,700,500);
        canvas_1 -> cd();

        RD1 -> SetTitle("COMPARISON SumPt CR and SR");
        RD1 -> GetXaxis()->SetTitle("SumPt (GeV)");
        RD1 -> SetLineColor(4);
        RD1 -> SetLineWidth(2);
        RD1 -> Draw("");

        RD2 -> SetLineColor(2);
        RD2 -> SetLineWidth(1);
        RD2 -> Draw("same");

  TLegend* legend = new TLegend(0.62,0.8,0.894,0.9);
  legend->AddEntry( RD1, "SumPT_CR_800_1200_EF_j240_a4tc_EFFS", "l");
  legend->AddEntry( RD2, "SumPT_SR_1200PLUS_EF_j240_a4tc_EFFS", "l");
  legend->SetFillColor(0);
  legend->SetBorderSize(1);
  legend->Draw("");

  canvas_1 -> Update();
  canvas_1 ->SaveAs("/Users/aibutt/BLACKHOLE_ANALYSIS/DATA2011/non-commutative/SumPT_1_j240.gif");

}

But I am getting following error which I am not able to resolve:

root [0] .x COMPARISON_SCRIPT.C
Error: illegal pointer to class object RD2 0x0 147 COMPARISON_SCRIPT.C:24:
*** Interpreter error recovered ***
root [1]

And it plots only the first histogram that I am declaring in my code as RD1.

Cheers
Aatif

2

And what do you get when you try to:
READ_File1->ls();

BTW. See also notes about “GetObject” in http://root.cern.ch/root/html/TDirectoryFile.html#TDirectoryFile:Get