//Plotting two graphs with different y scale on one root canvas

{
   gROOT->Reset();
   c1 = new TCanvas("c1","cross-section with photon flux",1500,500);
   TPad *pad = new TPad("pad","",0,0,1,1);
//   pad->SetFillColor(42);
   pad->SetGrid();
   pad->Draw();
   pad->cd();

   // draw a frame to define the range
   TH1F *hr = c1->DrawFrame(0,0,30,170);			//(x-axis initial, y- axis initial, x-axis final, y-axis final)
   hr->SetXTitle("photon energy (MeV)");
   hr->SetYTitle("Microscopic cross-section (mb)");
   pad->GetFrame()->SetFillColor(21);
   pad->GetFrame()->SetBorderSize(12);

  // create first graph
  g1= new TGraph("cross_section.dat");				//Create a graph for a text file saved in the same directory as this program
  g1-> SetMarkerStyle(5);					//Marker styles can be found under view toolbar in the canvas
  g1-> Draw ("CL");						//Draw with Axes, Points and Curve. If you used L in the place of C, It will join the data points with straight lines and not smooth curves.


   //create a transparent pad drawn on top of the main pad
   c1->cd();
   TPad *overlay = new TPad("overlay","",0,0,1,1);
   overlay->SetFillStyle(4000);
   overlay->SetFillColor(0);
   overlay->SetFrameFillStyle(4000);
   overlay->Draw();
   overlay->cd();
  
   //Create the second graph
   g2= new TGraph("phflx.dat");
   g2->SetMarkerColor(kRed);
   g2->SetMarkerStyle(5);
   g2->SetName("g2");
   TH1F *hframe = overlay->DrawFrame(0,0,30,10000000);		//(xmin, ymin(second y axis), xmax, ymax(second y axis))
   hframe->GetXaxis()->SetLabelOffset(99);
   hframe->GetYaxis()->SetLabelOffset(99);
   g2->Draw("CL");

   //Draw an axis on the right side
//   TF1 *f3=new TF1("f3","log10(x)",1,1000);
//   TGaxis *axis = new TGaxis(30,0,10000000,0,"f3",80506,"G");
   TGaxis *axis = new TGaxis(30,0,30, 10000000,0,10000000,80506,"+L");	//(xmax, xmin, xmax, ymax(second y axis), ymin, ymax(second y axis),type, marker place)
//   overlay->SetLogy(1);
   axis->SetLineColor(kRed);
   axis->SetLabelColor(kRed);
   axis->Draw();

}