Fix drawing in df104 tutorial

1. Disable automatic drawing when fitting
2. Draw data histogram only when all settings are done
3. Use TH1I instead of TF1 for axis drawing in lower pad

Created canvas can be stored and read back properly from ROOT file

tutorials/dataframe/df104_HiggsToTwoPhotons.py

@@ -113,7 +113,6 @@ upper_pad.Draw()
 lower_pad.Draw()
 
 # Fit signal + background model to data
-upper_pad.cd()
 fit = ROOT.TF1("fit", "([0]+[1]*x+[2]*x^2+[3]*x^3)+[4]*exp(-0.5*((x-[5])/[6])^2)", 105, 160)
 fit.FixParameter(5, 125.0)
 fit.FixParameter(4, 119.1)
@@ -121,30 +120,33 @@ fit.FixParameter(6, 2.39)
 fit.SetLineColor(2)
 fit.SetLineStyle(1)
 fit.SetLineWidth(2)
-data.Fit("fit", "", "E SAME", 105, 160)
-fit.Draw("SAME")
-
-# Draw background
-bkg = ROOT.TF1("bkg", "([0]+[1]*x+[2]*x^2+[3]*x^3)", 105, 160)
-for i in range(4):
-    bkg.SetParameter(i, fit.GetParameter(i))
-bkg.SetLineColor(4)
-bkg.SetLineStyle(2)
-bkg.SetLineWidth(2)
-bkg.Draw("SAME")
+data.Fit("fit", "0", "", 105, 160)
 
 # Draw data
+upper_pad.cd()
 data.SetMarkerStyle(20)
 data.SetMarkerSize(1.2)
 data.SetLineWidth(2)
 data.SetLineColor(ROOT.kBlack)
-data.Draw("E SAME")
 data.SetMinimum(1e-3)
 data.SetMaximum(8e3)
 data.GetYaxis().SetLabelSize(0.045)
 data.GetYaxis().SetTitleSize(0.05)
 data.SetStats(0)
 data.SetTitle("")
+data.Draw("E")
+
+# Draw fit
+fit.Draw("SAME")
+
+# Draw background
+bkg = ROOT.TF1("bkg", "([0]+[1]*x+[2]*x^2+[3]*x^3)", 105, 160)
+for i in range(4):
+    bkg.SetParameter(i, fit.GetParameter(i))
+bkg.SetLineColor(4)
+bkg.SetLineStyle(2)
+bkg.SetLineWidth(2)
+bkg.Draw("SAME")
 
 # Scale simulated events with luminosity * cross-section / sum of weights
 # and merge to single Higgs signal
@@ -158,7 +160,7 @@ higgs.Draw("HIST SAME")
 # Draw ratio
 lower_pad.cd()
 
-ratiobkg = ROOT.TF1("zero", "0", 105, 160)
+ratiobkg = ROOT.TH1I("zero", "", 100, 105, 160)
 ratiobkg.SetLineColor(4)
 ratiobkg.SetLineStyle(2)
 ratiobkg.SetLineWidth(2)
@@ -175,7 +177,7 @@ ratiobkg.GetYaxis().SetTitleOffset(0.7)
 ratiobkg.GetYaxis().SetNdivisions(503, False)
 ratiobkg.GetYaxis().ChangeLabel(-1, -1, 0)
 ratiobkg.GetXaxis().SetTitle("m_{#gamma#gamma} [GeV]")
-ratiobkg.Draw()
+ratiobkg.Draw("AXIS")
 
 ratiosig = ROOT.TH1F("ratiosig", "ratiosig", 5500, 105, 160)
 ratiosig.Eval(fit)
@@ -187,9 +189,9 @@ ratiosig.Draw("SAME")
 
 ratiodata = data.Clone()
 ratiodata.Add(bkg, -1)
-ratiodata.Draw("E SAME")
 for i in range(1, data.GetNbinsX()):
     ratiodata.SetBinError(i, data.GetBinError(i))
+ratiodata.Draw("E SAME")
 
 # Add legend
 upper_pad.cd()
@@ -203,7 +205,7 @@ legend.AddEntry(data, "Data" ,"lep")
 legend.AddEntry(bkg, "Background", "l")
 legend.AddEntry(fit, "Signal + Bkg.", "l")
 legend.AddEntry(higgs, "Signal", "l")
-legend.Draw("SAME")
+legend.Draw()
 
 # Add ATLAS label
 text = ROOT.TLatex()