rf509_wsinteractive.py

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## \file
## \ingroup tutorial_roofit
## \notebook
##
## Organization and simultaneous fits: easy interactive access to workspace contents - CINT to CLING code migration
##
## \macro_code
##
## \date February 2018
## \author Clemens Lange, Wouter Verkerke (C++ version)

import ROOT


def fillWorkspace(w):
    # Create pdf and fill workspace
    # --------------------------------------------------------

    # 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, 0, 10)
    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)

    # Build Chebychev polynomial p.d.f.
    a0 = ROOT.RooRealVar("a0", "a0", 0.5, 0., 1.)
    a1 = ROOT.RooRealVar("a1", "a1", -0.2, 0., 1.)
    bkg = ROOT.RooChebychev("bkg", "Background", x, ROOT.RooArgList(a0, a1))

    # 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))

    # 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))

    getattr(w, 'import')(model)


# Create and fill workspace
# ------------------------------------------------


# Create a workspace named 'w'
# With CINT w could exports its contents to
# a same-name C++ namespace in CINT 'namespace w'.
# but self does not work anymore in CLING.
# so self tutorial is an example on how to
# change the code
w = ROOT.RooWorkspace("w", ROOT.kTRUE)

# Fill workspace with p.d.f. and data in a separate function
fillWorkspace(w)

# Print workspace contents
w.Print()

# self does not work anymore with CLING
# use normal workspace functionality

# Use workspace contents
# ----------------------------------------------

# Old syntax to use the name space prefix operator to access the workspace contents
#
#d = w.model.generate(w.x,1000)
#r = w.model.fitTo(*d)

# use normal workspace methods
model = w.pdf("model")
x = w.var("x")

d = model.generate(ROOT.RooArgSet(x), 1000)
r = model.fitTo(d)

# old syntax to access the variable x
# frame = w.x.frame()

frame = x.frame()
d.plotOn(frame)

# OLD syntax to ommit x.
# NB: The 'w.' prefix can be omitted if namespace w is imported in local namespace
# in the usual C++ way
#
# using namespace w
# model.plotOn(frame)
# model.plotOn(frame, ROOT.RooFit.Components(bkg), ROOT.RooFit.LineStyle(ROOT.kDashed))

# correct syntax
bkg = w.pdf("bkg")
model.plotOn(frame)
ras_bkg = ROOT.RooArgSet(bkg)
model.plotOn(frame, ROOT.RooFit.Components(ras_bkg),
             ROOT.RooFit.LineStyle(ROOT.kDashed))

# Draw the frame on the canvas
c = ROOT.TCanvas("rf509_wsinteractive", "rf509_wsinteractive", 600, 600)
ROOT.gPad.SetLeftMargin(0.15)
frame.GetYaxis().SetTitleOffset(1.4)
frame.Draw()

c.SaveAs("rf509_wsinteractive.png")