void plot_t_slope_dep_comp(){
  double Eg[15],dEg[15];
  for (int i=0;i<15;i++){
    Eg[i]=2.9+0.2*i;
    dEg[i]=0.1;
  }
  double tslope[15];
  double dtslope[15];

  ifstream in_file("phi_parms.dat");
  for (int i=0;i<15;i++){
    double dummy;
    in_file >> dummy;
    in_file >> dummy;
    in_file >> dummy;
    in_file >> tslope[i];
    in_file >> dtslope[i];
  }
  for (int i=0;i<15;i++) tslope[i]*=-1.;

  double tslope1[15];
  double dtslope1[15];

  ifstream in_file1("phi_parms_method1.dat");
  for (int i=0;i<15;i++){
    double dummy;
    in_file1 >> dummy;
    in_file1 >> dummy;
    in_file1 >> dummy;
    in_file1 >> tslope1[i];
    in_file1 >> dtslope1[i];
  }
  for (int i=0;i<15;i++) tslope1[i]*=-1.;

  TH2F *h=new TH2F("h","t-slope dependence",15,2.6,5.8,10,0,6);
  h->SetXTitle("E_{#gamma} [GeV]");
  h->SetYTitle("t-slope parameter A [GeV^{-2}]");
  h->Draw();
  TGraphErrors *g1=new TGraphErrors(15,Eg,tslope,0,dtslope);
  g1->SetMarkerColor(4);
  g1->SetMarkerStyle(21);
  g1->SetLineColor(4);
  g1->Draw("p");
  
  TGraphErrors *g3=new TGraphErrors(15,Eg,tslope1,0,dtslope1);
  g3->SetMarkerColor(2);
  g3->SetMarkerStyle(20);
  g3->SetLineColor(2);
  g3->Draw("p");


  double ballamE[2]={2.8,4.7};
  double ballamdE[2]={0.5,0.6};
  double ballamA[2]={3.7,3.7};
  double ballamdA[2]={1.2,1.0};
  TGraphErrors *g2=new TGraphErrors(2,ballamE,ballamA,ballamdE,ballamdA);
  g2->SetLineColor(8);
  g2->SetMarkerColor(8);
  g2->SetMarkerStyle(22);
  g2->Draw("p");

  TLegend *legend =new TLegend(0.5,0.15,0.8,0.35);
  legend->AddEntry(g3,"Method 1","p"); 
  legend->AddEntry(g1,"Method 2","p");
  legend->AddEntry(g2,"Ballam 1973","p");
  legend->Draw();

}