hist031_TRatioPlot_residual_fit.py

## \file
## \ingroup tutorial_hist
## \notebook
## Example which shows how you can get the graph of the lower plot and set the y axis range for it.
##
## Since the lower plot is not created until `TRatioPlot::Draw` is called, you can only use the method
## afterwards.
## Inspired by the tutorial of Paul Gessinger.
##
## \macro_image
## \macro_code
##
## \author Alberto Ferro

import ROOT

ROOT.gStyle.SetOptStat(0)
c1 = ROOT.TCanvas("c1", "fit residual simple")
c1.SetLogy()

h1 = ROOT.TH1D("h1", "h1", 50, -5, 5)
h1.FillRandom("gaus", 2000)
h1.Fit("gaus")
h1.SetMinimum(0.001)
h1.GetXaxis().SetTitle("x")
h1.GetYaxis().SetTitle("y")

rp1 = ROOT.TRatioPlot(h1)
rp1.Draw()
rp1.GetLowerRefGraph().SetMinimum(-2)
rp1.GetLowerRefGraph().SetMaximum(2)

c1.Update()