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Reference Guide
rf206_treevistools.py
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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(
29 "sig1frac", "fraction of component 1 in signal", 0.8, 0., 1.)
30sig = ROOT.RooAddPdf(
31 "sig", "Signal", ROOT.RooArgList(sig1, sig2), ROOT.RooArgList(sig1frac))
32
33# Build Chebychev polynomial pdf
34a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0., 1.)
35a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0., 1.)
36bkg1 = ROOT.RooChebychev("bkg1", "Background 1",
37 x, ROOT.RooArgList(a0, a1))
38
39# Build expontential pdf
40alpha = ROOT.RooRealVar("alpha", "alpha", -1)
41bkg2 = ROOT.RooExponential("bkg2", "Background 2", x, alpha)
42
43# Sum the background components into a composite background pdf
44bkg1frac = ROOT.RooRealVar(
45 "bkg1frac", "fraction of component 1 in background", 0.2, 0., 1.)
46bkg = ROOT.RooAddPdf(
47 "bkg", "Signal", ROOT.RooArgList(bkg1, bkg2), ROOT.RooArgList(bkg1frac))
48
49# Sum the composite signal and background
50bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0., 1.)
51model = ROOT.RooAddPdf(
52 "model", "g1+g2+a", ROOT.RooArgList(bkg, sig), ROOT.RooArgList(bkgfrac))
53
54# Print composite tree in ASCII
55# -----------------------------------------------------------
56
57# Print tree to stdout
58model.Print("t")
59
60# Print tree to file
61model.printCompactTree("", "rf206_asciitree.txt")
62
63# Draw composite tree graphically
64# -------------------------------------------------------------
65
66# Print GraphViz DOT file with representation of tree
67model.graphVizTree("rf206_model.dot")
68
69# Make graphic output file with one of the GraphViz tools
70# (freely available from www.graphviz.org)
71#
72# 'Top-to-bottom graph'
73# unix> dot -Tgif -o rf207_model_dot.gif rf207_model.dot
74#
75# 'Spring-model graph'
76# unix> fdp -Tgif -o rf207_model_fdp.gif rf207_model.dot