rf206_treevistools.py

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## \file
## \ingroup tutorial_roofit
## \notebook -nodraw
## Addition and convolution: tools for visualization of ROOT.RooAbsArg expression trees
##
## \macro_code
##
## \date February 2018
## \author Clemens Lange, Wouter Verkerke (C++ version)
 
import ROOT
 
# Set up composite pdf
# --------------------------------------
 
# Declare observable x
x = ROOT.RooRealVar("x", "x", 0, 10)
 
# Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and
# their parameters
mean = ROOT.RooRealVar("mean", "mean of gaussians", 5)
sigma1 = ROOT.RooRealVar("sigma1", "width of gaussians", 0.5)
sigma2 = ROOT.RooRealVar("sigma2", "width of gaussians", 1)
sig1 = ROOT.RooGaussian("sig1", "Signal component 1", x, mean, sigma1)
sig2 = ROOT.RooGaussian("sig2", "Signal component 2", x, mean, sigma2)
 
# Sum the signal components into a composite signal p.d.f.
sig1frac = ROOT.RooRealVar(
    "sig1frac", "fraction of component 1 in signal", 0.8, 0., 1.)
sig = ROOT.RooAddPdf(
    "sig", "Signal", ROOT.RooArgList(sig1, sig2), ROOT.RooArgList(sig1frac))
 
# Build Chebychev polynomial p.d.f.
a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0., 1.)
a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0., 1.)
bkg1 = ROOT.RooChebychev("bkg1", "Background 1",
                         x, ROOT.RooArgList(a0, a1))
 
# Build expontential pdf
alpha = ROOT.RooRealVar("alpha", "alpha", -1)
bkg2 = ROOT.RooExponential("bkg2", "Background 2", x, alpha)
 
# Sum the background components into a composite background p.d.f.
bkg1frac = ROOT.RooRealVar(
    "bkg1frac", "fraction of component 1 in background", 0.2, 0., 1.)
bkg = ROOT.RooAddPdf(
    "bkg", "Signal", ROOT.RooArgList(bkg1, bkg2), ROOT.RooArgList(bkg1frac))
 
# Sum the composite signal and background
bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0., 1.)
model = ROOT.RooAddPdf(
    "model", "g1+g2+a", ROOT.RooArgList(bkg, sig), ROOT.RooArgList(bkgfrac))
 
# Print composite tree in ASCII
# -----------------------------------------------------------
 
# Print tree to stdout
model.Print("t")
 
# Print tree to file
model.printCompactTree("", "rf206_asciitree.txt")
 
# Draw composite tree graphically
# -------------------------------------------------------------
 
# Print GraphViz DOT file with representation of tree
model.graphVizTree("rf206_model.dot")
 
# Make graphic output file with one of the GraphViz tools
# (freely available from www.graphviz.org)
#
# 'Top-to-bottom graph'
# unix> dot -Tgif -o rf207_model_dot.gif rf207_model.dot
#
# 'Spring-model graph'
# unix> fdp -Tgif -o rf207_model_fdp.gif rf207_model.dot