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Reference Guide
rf509_wsinteractive.py
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1 ## \file
2 ## \ingroup tutorial_roofit
3 ## \notebook
4 ## Organization and simultaneous fits: easy interactive access to workspace contents - CINT
5 ## to CLING code migration
6 ##
7 ## \macro_code
8 ##
9 ## \date February 2018
10 ## \authors Clemens Lange, Wouter Verkerke (C++ version)
11 
12 import ROOT
13 
14 
15 def fillWorkspace(w):
16  # Create pdf and fill workspace
17  # --------------------------------------------------------
18 
19  # Declare observable x
20  x = ROOT.RooRealVar("x", "x", 0, 10)
21 
22  # Create two Gaussian PDFs g1(x,mean1,sigma) anf g2(x,mean2,sigma) and
23  # their parameters
24  mean = ROOT.RooRealVar("mean", "mean of gaussians", 5, 0, 10)
25  sigma1 = ROOT.RooRealVar("sigma1", "width of gaussians", 0.5)
26  sigma2 = ROOT.RooRealVar("sigma2", "width of gaussians", 1)
27 
28  sig1 = ROOT.RooGaussian("sig1", "Signal component 1", x, mean, sigma1)
29  sig2 = ROOT.RooGaussian("sig2", "Signal component 2", x, mean, sigma2)
30 
31  # Build Chebychev polynomial pdf
32  a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0., 1.)
33  a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0., 1.)
34  bkg = ROOT.RooChebychev("bkg", "Background", x, ROOT.RooArgList(a0, a1))
35 
36  # Sum the signal components into a composite signal pdf
37  sig1frac = ROOT.RooRealVar(
38  "sig1frac", "fraction of component 1 in signal", 0.8, 0., 1.)
39  sig = ROOT.RooAddPdf(
40  "sig", "Signal", ROOT.RooArgList(
41  sig1, sig2), ROOT.RooArgList(sig1frac))
42 
43  # Sum the composite signal and background
44  bkgfrac = ROOT.RooRealVar("bkgfrac", "fraction of background", 0.5, 0., 1.)
45  model = ROOT.RooAddPdf(
46  "model",
47  "g1+g2+a",
48  ROOT.RooArgList(
49  bkg,
50  sig),
51  ROOT.RooArgList(bkgfrac))
52 
53  w.Import(model)
54 
55 
56 # Create and fill workspace
57 # ------------------------------------------------
58 
59 
60 # Create a workspace named 'w'
61 # With CINT w could exports its contents to
62 # a same-name C++ namespace in CINT 'namespace w'.
63 # but self does not work anymore in CLING.
64 # so self tutorial is an example on how to
65 # change the code
66 w = ROOT.RooWorkspace("w", ROOT.kTRUE)
67 
68 # Fill workspace with pdf and data in a separate function
69 fillWorkspace(w)
70 
71 # Print workspace contents
72 w.Print()
73 
74 # self does not work anymore with CLING
75 # use normal workspace functionality
76 
77 # Use workspace contents
78 # ----------------------------------------------
79 
80 # Old syntax to use the name space prefix operator to access the workspace contents
81 #
82 #d = w.model.generate(w.x,1000)
83 #r = w.model.fitTo(*d)
84 
85 # use normal workspace methods
86 model = w.pdf("model")
87 x = w.var("x")
88 
89 d = model.generate(ROOT.RooArgSet(x), 1000)
90 r = model.fitTo(d)
91 
92 # old syntax to access the variable x
93 # frame = w.x.frame()
94 
95 frame = x.frame()
96 d.plotOn(frame)
97 
98 # OLD syntax to ommit x.
99 # NB: The 'w.' prefix can be omitted if namespace w is imported in local namespace
100 # in the usual C++ way
101 #
102 # using namespace w
103 # model.plotOn(frame)
104 # model.plotOn(frame, ROOT.RooFit.Components(bkg), ROOT.RooFit.LineStyle(ROOT.kDashed))
105 
106 # correct syntax
107 bkg = w.pdf("bkg")
108 model.plotOn(frame)
109 ras_bkg = ROOT.RooArgSet(bkg)
110 model.plotOn(frame, ROOT.RooFit.Components(ras_bkg),
111  ROOT.RooFit.LineStyle(ROOT.kDashed))
112 
113 # Draw the frame on the canvas
114 c = ROOT.TCanvas("rf509_wsinteractive", "rf509_wsinteractive", 600, 600)
115 ROOT.gPad.SetLeftMargin(0.15)
116 frame.GetYaxis().SetTitleOffset(1.4)
117 frame.Draw()
118 
119 c.SaveAs("rf509_wsinteractive.png")