Port of ratioplot.C to python

tutorials/pyroot/ratioplot.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python
+# ratioplot.py - example displaying two histograms and their ratio
+#   Original c++ code: Olivier Couet
+#   Python port: Michael Moran
+
+
+from ROOT import TCanvas, TColor, TGaxis, TH1F, TPad
+from ROOT import kBlack, kBlue, kRed
+
+
+def createH1():
+  h1 = TH1F("h1", ("Two gaussian plots and their ratio; x title; h1 and h2"
+            " histograms"), 100, -5, 5)
+  h1.SetLineColor(kBlue+1)
+  h1.SetLineWidth(2)
+  h1.FillRandom("gaus")
+  h1.GetYaxis().SetTitleSize(20)
+  h1.GetYaxis().SetTitleFont(43)
+  h1.GetYaxis().SetTitleOffset(1.55)
+  h1.SetStats(0)
+  return h1
+
+
+def createH2():
+  h2 = TH1F("h2", "h2", 100, -5, 5)
+  h2.FillRandom("gaus")
+  h2.SetLineColor(kRed)
+  h2.SetLineWidth(2)
+  return h2
+
+
+def createRatio(h1, h2):
+  h3 = h1.Clone("h3")
+  h3.SetLineColor(kBlack)
+  h3.SetMarkerStyle(21)
+  h3.SetTitle("")
+  h3.SetMinimum(0.8)
+  h3.SetMaximum(1.35)
+  # Set up plot for markers and errors
+  h3.Sumw2()
+  h3.SetStats(0)
+  h3.Divide(h2)
+
+  # Adjust y-axis settings
+  y = h3.GetYaxis()
+  y.SetTitle("ratio h1/h2 ")
+  y.SetNdivisions(505)
+  y.SetTitleSize(20)
+  y.SetTitleFont(43)
+  y.SetTitleOffset(1.55)
+  y.SetLabelFont(43)
+  y.SetLabelSize(15)
+
+  # Adjust x-axis settings
+  x = h3.GetXaxis()
+  x.SetTitleSize(20)
+  x.SetTitleFont(43)
+  x.SetTitleOffset(4.0)
+  x.SetLabelFont(43)
+  x.SetLabelSize(15)
+
+  return h3
+
+
+def createCanvasPads():
+  c = TCanvas("c", "canvas", 800, 800)
+  # Upper histogram plot is pad1
+  pad1 = TPad("pad1", "pad1", 0, 0.3, 1, 1.0)
+  pad1.SetBottomMargin(0)  # joins upper and lower plot
+  pad1.SetGridx()
+  pad1.Draw()
+  # Lower ratio plot is pad2
+  c.cd()  # returns to main canvas before defining pad2
+  pad2 = TPad("pad2", "pad2", 0, 0.05, 1, 0.3)
+  pad2.SetTopMargin(0)  # joins upper and lower plot
+  pad2.SetBottomMargin(0.2)
+  pad2.SetGridx()
+  pad2.Draw()
+
+  return c, pad1, pad2
+
+
+def ratioplot():
+  # create required parts
+  h1 = createH1()
+  h2 = createH2()
+  h3 = createRatio(h1, h2)
+  c, pad1, pad2 = createCanvasPads()
+
+  # draw everything
+  pad1.cd()
+  h1.Draw()
+  h2.Draw("same")
+  # to avoid clipping the bottom zero, redraw a small axis
+  h1.GetYaxis().SetLabelSize(0.0)
+  axis = TGaxis(-5, 20, -5, 220, 20, 220, 510, "")
+  axis.SetLabelFont(43)
+  axis.SetLabelSize(15)
+  axis.Draw()
+  pad2.cd()
+  h3.Draw("ep")
+
+  # To hold window open when running from command line
+#  text = raw_input()
+
+
+if __name__ == "__main__":
+  ratioplot()