hist029_TRatioPlot_simple.py

## \ingroup tutorial_hist

## \notebook

## 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.

##

## \macro_image

## \macro_code

##

## \author Alberto Ferro

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()