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ratioplot.py File Reference

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 ratioplot
 

Detailed Description

View in nbviewer Open in SWAN Display two histograms and their ratio.

This program illustrates how to plot two histograms and their ratio on the same canvas. Original macro by Olivier Couet.

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__":
Author
Michael Moran

Definition in file ratioplot.py.

TPad
Definition: TPad.h:26
TCanvas
Definition: TCanvas.h:23
TGaxis
Definition: TGaxis.h:23
ratioplot
Definition: ratioplot.py:1
TH1F
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:572