void xrangeIssue ()
{
  TF1 *f1 = new TF1("f1","TMath::Exp(-x)",0,10);
  TF1 *f2 = new TF1("f2","TMath::Exp(-x)",0,20);
  TF1 *f3 = new TF1("f3","TMath::Exp(-x)",0,30);
  double x[5], y[5];
  for(Int_t i = 0; i < 5; i++) {x[i]=0.5*(1+i); y[i]=f1->Eval(x[i]);}
  TGraph *g1 = new TGraph(5,x,y); g1->SetMaximum(0.76); g1->SetMinimum(0.05); g1->SetTitle("for xmax=10");
  TGraph *g2 = (TGraph*)g1->Clone("g2"); g2->SetTitle("for xmax=20");
  TGraph *g3 = (TGraph*)g1->Clone("g3"); g3->SetTitle("for xmax=30");
  TCanvas *c1 = new TCanvas("c1","c1", 1100,500);
  c1->Divide(3,1);
  c1->cd(1);
  g1->Draw("a*");
  f1->Draw("same");
  c1->cd(2);
  g2->Draw("a*");
  f2->Draw("same");
  c1->cd(3);
  g3->Draw("a*");
  f3->Draw("same");
}