rf108_plotbinning.py

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## \file
## \ingroup tutorial_roofit
## \notebook
## Basic functionality: plotting unbinned data with alternate and variable binnings
##
## \macro_code
##
## \date February 2018
## \author Clemens Lange, Wouter Verkerke (C++ version)

import ROOT

# Set up model
# ---------------------

# Build a B decay p.d.f with mixing
dt = ROOT.RooRealVar("dt", "dt", -20, 20)
dm = ROOT.RooRealVar("dm", "dm", 0.472)
tau = ROOT.RooRealVar("tau", "tau", 1.547)
w = ROOT.RooRealVar("w", "mistag rate", 0.1)
dw = ROOT.RooRealVar("dw", "delta mistag rate", 0.)

mixState = ROOT.RooCategory("mixState", "B0/B0bar mixing state")
mixState.defineType("mixed", -1)
mixState.defineType("unmixed", 1)
tagFlav = ROOT.RooCategory("tagFlav", "Flavour of the tagged B0")
tagFlav.defineType("B0", 1)
tagFlav.defineType("B0bar", -1)

# Build a gaussian resolution model
dterr = ROOT.RooRealVar("dterr", "dterr", 0.1, 1.0)
bias1 = ROOT.RooRealVar("bias1", "bias1", 0)
sigma1 = ROOT.RooRealVar("sigma1", "sigma1", 0.1)
gm1 = ROOT.RooGaussModel("gm1", "gauss model 1", dt, bias1, sigma1)

# Construct Bdecay (x) gauss
bmix = ROOT.RooBMixDecay("bmix", "decay", dt, mixState, tagFlav,
                         tau, dm, w, dw, gm1, ROOT.RooBMixDecay.DoubleSided)

# Sample data from model
# --------------------------------------------

# Sample 2000 events in (dt,mixState,tagFlav) from bmix
data = bmix.generate(ROOT.RooArgSet(dt, mixState, tagFlav), 2000)

# Show dt distribution with custom binning
# -------------------------------------------------------------------------------

# Make plot of dt distribution of data in range (-15,15) with fine binning
# for dt>0 and coarse binning for dt<0

# Create binning object with range (-15,15)
tbins = ROOT.RooBinning(-15, 15)

# Add 60 bins with uniform spacing in range (-15,0)
tbins.addUniform(60, -15, 0)

# Add 15 bins with uniform spacing in range (0,15)
tbins.addUniform(15, 0, 15)

# Make plot with specified binning
dtframe = dt.frame(ROOT.RooFit.Range(-15, 15),
                   ROOT.RooFit.Title("dt distribution with custom binning"))
data.plotOn(dtframe, ROOT.RooFit.Binning(tbins))
bmix.plotOn(dtframe)

# NB: Note that bin density for each bin is adjusted to that of default frame binning as shown
# in Y axis label (100 bins -. Events/0.4*Xaxis-dim) so that all bins
# represent a consistent density distribution

# Show mixstate asymmetry with custom binning
# ------------------------------------------------------------------------------------

# Make plot of dt distribution of data asymmetry in 'mixState' with
# variable binning

# Create binning object with range (-10,10)
abins = ROOT.RooBinning(-10, 10)

# Add boundaries at 0, (-1,1), (-2,2), (-3,3), (-4,4) and (-6,6)
abins.addBoundary(0)
abins.addBoundaryPair(1)
abins.addBoundaryPair(2)
abins.addBoundaryPair(3)
abins.addBoundaryPair(4)
abins.addBoundaryPair(6)

# Create plot frame in dt
aframe = dt.frame(ROOT.RooFit.Range(-10, 10), ROOT.RooFit.Title(
    "mixState asymmetry distribution with custom binning"))

# Plot mixState asymmetry of data with specified customg binning
data.plotOn(aframe, ROOT.RooFit.Asymmetry(
    mixState), ROOT.RooFit.Binning(abins))

# Plot corresponding property of p.d.f
bmix.plotOn(aframe, ROOT.RooFit.Asymmetry(mixState))

# Adjust vertical range of plot to sensible values for an asymmetry
aframe.SetMinimum(-1.1)
aframe.SetMaximum(1.1)

# NB: For asymmetry distributions no density corrects are needed (and are
# thus not applied)

# Draw plots on canvas
c = ROOT.TCanvas("rf108_plotbinning", "rf108_plotbinning", 800, 400)
c.Divide(2)
c.cd(1)
ROOT.gPad.SetLeftMargin(0.15)
dtframe.GetYaxis().SetTitleOffset(1.6)
dtframe.Draw()
c.cd(2)
ROOT.gPad.SetLeftMargin(0.15)
aframe.GetYaxis().SetTitleOffset(1.6)
aframe.Draw()

c.SaveAs("rf108_plotbinning.png")