Using THStack for histograms

tracking/scripts/rec_central_electrons.cxx

@@ -134,9 +134,13 @@ int rec_central_electrons(const char* fname = "topside/rec_central_electrons.roo
   c->SaveAs("results/tracking/rec_central_electrons_pTracks.png");
   c->SaveAs("results/tracking/rec_central_electrons_pTracks.pdf");
 
-  h_delta_p->DrawCopy();
-  h_delta_p1->SetLineColor(2);
-  h_delta_p1->DrawCopy("same");
+  THStack * hs = new THStack("hs_delta_p","; GeV/c "); 
+  TH1D* h1 = (TH1D*) h_delta_p->Clone();
+  hs->Add(h1);
+  h1 = (TH1D*) h_delta_p1->Clone();
+  h1->SetLineColor(2);
+  hs->Add(h1);
+  hs->Draw("nostack");
   c->SaveAs("results/tracking/rec_central_electrons_delta_p.png");
   c->SaveAs("results/tracking/rec_central_electrons_delta_p.pdf");