// Reads the points from a txt file and produces a simple comparison graph.
void read_graph_txt_AMPT_data()
{
   auto c=new TCanvas();
   //c->SetGridy();
   c->SetLogy();

   TGraphErrors graph1("./data.txt","%lg %lg %lg 0");     // * means not select this column of data
   TGraphErrors graph2("./ALICE.txt","%lg %lg %lg 0");     // * means not select this column of data

   graph1.SetMarkerStyle(20);
   graph1.SetMarkerColor(kBlue);
   //graph1.GetYaxis()->SetRangeUser(10e-10, 4);
   
   graph2.SetMarkerStyle(20);
   graph2.SetMarkerColor(kRed);
   //graph2.GetYaxis()->SetRangeUser(10e-10, 4);
   
   TMultiGraph mg;
   mg.Add(&graph1);
   mg.Add(&graph2);
   mg.GetXaxis()->SetTitle("p_{T}(GeV)");
   mg.GetYaxis()->SetTitle("dN/dp_{T}(GeV^{2})");
   mg.GetXaxis()->CenterTitle();
   mg.GetYaxis()->CenterTitle();
   mg.GetYaxis()->SetRangeUser(10e-10, 4);
   mg.SetMinimum(0.001);
   mg.DrawClone("ALP");
}