{

  graph = new TGraph;
  graph->SetPoint(graph->GetN(), 1, 2.3);
  graph->SetPoint(graph->GetN(), 2, 0.8);
  graph->SetPoint(graph->GetN(), 3, -4);
  graph->Draw("AP");
  graph->SetMarkerStyle(21);
  graph->GetYaxis()->SetRangeUser(-10, 10);
  graph->GetXaxis()->SetTitle("Run number");
  graph->GetYaxis()->SetTitle("z (cm)");
  graph->SetTitle("Average vertex position");

}