void combined()
{
 TCanvas *c1= new TCanvas("c1","comparison graph of D0 pT spectra",700,500);
 c1->GetFrame()->SetBorderSize(12);   
  
  const Int_t n = 9;      
  Float_t x1[n] = {0.179335, 0.301069, 0.538599, 0.9038, 1.02257, 1.14133, 1.74109, 1.86283, 2.34086};     
  Float_t y1[n] = {0.0918845, 0.0876225, 0.0506373, 0.030292, 0.0137459, 0.0115158, 0.00747785, 0.00719284, 0.00577122};
  Float_t x2[n] = {1.5, 2.5, 3.5, 4.5, 5.5, 7,10, 14, 20};
  Float_t y2[n] = {2.65, 1.03, 0.262, 0.0744, 0.0226, 0.00646, 0.00152, 0.000258, 0.0000716};
  
  TGraph *gr1 = new TGraph(n,x1,y1);   
  TGraph *gr2 = new TGraph(n,x2,y2);
  gr1->SetMarkerColor(1);
  gr2->SetMarkerColor(4);
  
  gr1->Draw("AC*");             
  gr2->Draw("AC*");
 
  c1->Update();                   
  
}