## how do you superimpose graphs from different root files in C++/root

Hi,

ive created several graphs in different emacs files. I now want to superimpose them using code in a different emacs file. This is what i have done:

Code:
  //get the input files

TFile * inputfile = new TFile("p60.root","READ");
TFile * inputfile2 = new TFile("p20.root","READ");
TFile * inputfile3 = new TFile("p80.root","READ");
TFile * inputfile4 = new TFile("p40.root","READ");

//define canvas and plotting like before

/////////////////////////////////////////////////////////////////
//superposition of different energies of proton beam (one proton)
/////////////////////////////////////////////////////////////////

gStyle->SetPalette(1);

TCanvas* comp = new TCanvas("comp","",1100,1100);
comp->Clear();
comp->Divide(1,1);
//TGraph* g40 = (TGraph*) inputfile4 -> Get("g4");//bit in the bracket is the name of the histogram
TGraph* g20 = (TGraph*) inputfile2 -> Get("g4");
comp->cd(1);
g20->SetLineColor(2);//2=red
g20->GetXaxis()->SetTitle("x (mm)");//title
g20->GetYaxis()->SetTitle("energy deposited (Mev)");
g20->Draw();
g20->GetXaxis()->SetTitleOffset(0.9);//changes vertical postion of the title
g20->GetXaxis()->SetTitleSize(0.045);//changes size of xaxis title (default)
g20->GetXaxis()->SetLabelSize(0.04); //changes the size of numbers on xaxis
g40->Draw("sames");// the s at end means that can have multiple stats box
g60->Draw("sames");
g20->SetLineColor(3);//2=red
g80->Draw("sames");
g20->SetLineColor(4);//2=red

comp->Modified();
comp->Update();
TLegend* legends = new TLegend(0.130,0.828,0.436,0.980,"","brNDC"); // the numbers determine the position of the box
legends->SetFillColor(0);
comp->cd();