Detailed Description

Example creating a simple ratio plot of two histograms using the pois division option.

Two histograms are set up and filled with random numbers. The constructor of TRatioPlot takes the to histograms, name and title for the object, drawing options for the histograms (hist and E in this case) and a drawing option for the output graph. Inspired by the tutorial of Paul Gessinger.

 
import ROOT
 
ROOT.gStyle.SetOptStat(0)
 
c1 = ROOT.TCanvas("c1", "A ratio example")
h1 = ROOT.TH1D("h1", "h1", 50, 0, 10)
h2 = ROOT.TH1D("h2", "h2", 50, 0, 10)
f1 = ROOT.TF1("f1", "exp(- x/[0] )")
f1.SetParameter(0,3)
 
h1.FillRandom("f1",1900)
h2.FillRandom("f1", 2000)
h1.Sumw2()
h2.Scale(1.9/2.)
 
h1.GetXaxis().SetTitle("x")
h1.GetYaxis().SetTitle("y")
 
rp = ROOT.TRatioPlot(h1,h2)
 
c1.SetTicks(0,1)
rp.GetLowYaxis().SetNdivisions(505)
c1.Update()
c1.Draw()
rp.Draw()
 

Author: Alberto Ferro

Definition in file ratioplot1.py.