ROOT   Reference Guide
rf206_treevistools.py
Go to the documentation of this file.
1## \file
2## \ingroup tutorial_roofit
3## \notebook -nodraw
4## Addition and convolution: tools for visualization of ROOT.RooAbsArg expression trees
5##
6## \macro_code
7##
8## \date February 2018
9## \authors Clemens Lange, Wouter Verkerke (C++ version)
10
11import ROOT
12
13# Set up composite pdf
14# --------------------------------------
15
16# Declare observable x
17x = ROOT.RooRealVar("x", "x", 0, 10)
18
19# Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and
20# their parameters
21mean = ROOT.RooRealVar("mean", "mean of gaussians", 5)
22sigma1 = ROOT.RooRealVar("sigma1", "width of gaussians", 0.5)
23sigma2 = ROOT.RooRealVar("sigma2", "width of gaussians", 1)
24sig1 = ROOT.RooGaussian("sig1", "Signal component 1", x, mean, sigma1)
25sig2 = ROOT.RooGaussian("sig2", "Signal component 2", x, mean, sigma2)
26
27# Sum the signal components into a composite signal pdf
28sig1frac = ROOT.RooRealVar("sig1frac", "fraction of component 1 in signal", 0.8, 0.0, 1.0)
29sig = ROOT.RooAddPdf("sig", "Signal", [sig1, sig2], [sig1frac])
30
31# Build Chebychev polynomial pdf
32a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0.0, 1.0)
33a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0.0, 1.0)
34bkg1 = ROOT.RooChebychev("bkg1", "Background 1", x, [a0, a1])
35
36# Build expontential pdf
37alpha = ROOT.RooRealVar("alpha", "alpha", -1)
38bkg2 = ROOT.RooExponential("bkg2", "Background 2", x, alpha)
39
40# Sum the background components into a composite background pdf
41bkg1frac = ROOT.RooRealVar("bkg1frac", "fraction of component 1 in background", 0.2, 0.0, 1.0)
42bkg = ROOT.RooAddPdf("bkg", "Signal", [bkg1, bkg2], [bkg1frac])
43
44# Sum the composite signal and background
45bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0.0, 1.0)
46model = ROOT.RooAddPdf("model", "g1+g2+a", [bkg, sig], [bkgfrac])
47
48# Print composite tree in ASCII
49# -----------------------------------------------------------
50
51# Print tree to stdout
52model.Print("t")
53
54# Print tree to file
55model.printCompactTree("", "rf206_asciitree.txt")
56
57# Draw composite tree graphically
58# -------------------------------------------------------------
59
60# Print GraphViz DOT file with representation of tree
61model.graphVizTree("rf206_model.dot")
62
63# Make graphic output file with one of the GraphViz tools
64# (freely available from www.graphviz.org)
65#
66# 'Top-to-bottom graph'
67# unix> dot -Tgif -o rf207_model_dot.gif rf207_model.dot
68#
69# 'Spring-model graph'
70# unix> fdp -Tgif -o rf207_model_fdp.gif rf207_model.dot