ROOT   Reference Guide
rf502_wspacewrite.py
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1## \file
2## \ingroup tutorial_roofit
3## \notebook -nodraw
4## Organization and simultaneous fits: creating and writing a workspace
5##
6## \macro_code
7##
8## \date February 2018
9## \authors Clemens Lange, Wouter Verkerke (C++ version)
10
11import ROOT
12
13
14# Create model and dataset
15# -----------------------------------------------
16
17# Declare observable x
18x = ROOT.RooRealVar("x", "x", 0, 10)
19
20# Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and
21# their parameters
22mean = ROOT.RooRealVar("mean", "mean of gaussians", 5, 0, 10)
23sigma1 = ROOT.RooRealVar("sigma1", "width of gaussians", 0.5)
24sigma2 = ROOT.RooRealVar("sigma2", "width of gaussians", 1)
25
26sig1 = ROOT.RooGaussian("sig1", "Signal component 1", x, mean, sigma1)
27sig2 = ROOT.RooGaussian("sig2", "Signal component 2", x, mean, sigma2)
28
29# Build Chebychev polynomial pdf
30a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0.0, 1.0)
31a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0.0, 1.0)
32bkg = ROOT.RooChebychev("bkg", "Background", x, [a0, a1])
33
34# Sum the signal components into a composite signal pdf
35sig1frac = ROOT.RooRealVar("sig1frac", "fraction of component 1 in signal", 0.8, 0.0, 1.0)
36sig = ROOT.RooAddPdf("sig", "Signal", [sig1, sig2], [sig1frac])
37
38# Sum the composite signal and background
39bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0.0, 1.0)
40model = ROOT.RooAddPdf("model", "g1+g2+a", [bkg, sig], [bkgfrac])
41
42# Generate a data sample of 1000 events in x from model
43data = model.generate({x}, 1000)
44
45# Create workspace, import data and model
46# -----------------------------------------------------------------------------
47
48# Create a empty workspace
49w = ROOT.RooWorkspace("w", "workspace")
50
51# Import model and all its components into the workspace
52w.Import(model)
53
54# Import data into the workspace
55w.Import(data)
56
57# Print workspace contents
58w.Print()
59
60# Save workspace in file
61# -------------------------------------------
62
63# Save the workspace into a ROOT file
64w.writeToFile("rf502_workspace_py.root")