Inputting then superimposing two graphs (beginner)

ROOT
1

The issue is now solved. Thanks!

There are two graphs saved within .root files.
I am able to upload the graphs and individually open them. However, I haven’t been able to figure out how to superimpose them. Here’s what I have so far:

TFile f(“fig/myfig_data_pt.root”);
TGraphErrors gr1 = (TGraphErrors)f.Get(“MassPlot”);
TFile f(“fig/myfig_mc_pt.root”);
TGraphErrors gr2 = (TGraphErrors)f.Get(“MassPlot”);
gr1->Draw(“AP”);
gr2->Draw(“P”);

When I do this, all I get is the graph of gr2. Oddly enough, when I replace TGraphErrors with TGraph or even TH1D, I still get the graph. It’s also strange to me that when I try creating a canvas for the two graphs, the canvas loads separately, leaving me with an empty canvas and the gr2 graph.

Changing colors and marker style hasn’t helped either. Any suggestions?

2

Could you post your data file and the short script reproducing your problem?

Rene

3

Here’s how I wrote the canvas into a root file

  TCanvas *c2 = new TCanvas("Candidates by Pt Range","Candidates by Pt Range",10,10,700,500);

  TFile *MyFile = new TFile("fig/myfig_data_pt.root","RECREATE");
    Double_t x[5]={0.75,1.25,1.75,2.50,4.00};
    Double_t ex[5]={0,0,0,0,0};

 //normalize

/* Magnitude=sqrt(y[0]*y[0]+y[1]*y[1]+y[2]*y[2]+y[3]*y[3]+y[4]*y[4]);
for (n=0; n<5; n++) {
y[n] /= Magnitude; ey[n] /= Magnitude;}
*/
gr = new TGraphErrors(5,x,y,ex,ey);
gr->GetXaxis()->SetTitle(“Mean Pt Value”);
gr->SetLineColor(kRed);
gr->SetMarkerColor(kRed);
gr->SetMarkerStyle(24);
gr->Draw(“AP”);
c2->Update();
c2->Write(“MassPlot”);

y[5] and ey[5] were defined within the program. When I run the program, linux just responds, “Processing test.cxx” (test.cxx is the program’s name). Is this what you were asking for?

4

In the program save your graph with

TFile *MyFile = new TFile("fig/myfig_data_pt.root","RECREATE"); gr = new TGraphErrors(5,x,y,ex,ey); gr->GetXaxis()->SetTitle("Mean Pt Value"); gr->SetLineColor(kRed); gr->SetMarkerColor(kRed); gr->SetMarkerStyle(24); gr->Draw("AP"); c2->Update(); gr->Write("MassPlot");
In the reading program do:

TFile *f1 = TFile::Open("fig/myfig_data_pt.root"); TGraphErrors *gr1 = (TGraphErrors*)f1->Get("MassPlot"); TFile *f2 = TFile::Open("fig/myfig_mc_pt.root"); TGraphErrors *gr2 = (TGraphErrors*)f2->Get("MassPlot"); gr1->Draw("AP"); gr2->Draw("P");

Rene

5

Thanks! The program is working now that I saved the file as a graph rather than the canvas as you recommended.