doc/v632/rf401__importttreethx_8py.html

import ROOT

from array import array


def makeTH1(name, mean, sigma):

    """Create ROOT TH1 filled with a Gaussian distribution."""


    hh = ROOT.TH1D(name, name, 100, -10, 10)

    for i in range(1000):

        hh.Fill(ROOT.gRandom.Gaus(mean, sigma))


    return hh


def makeTTree():

    """Create ROOT ROOT.TTree filled with a Gaussian distribution in x and a uniform distribution in y."""


    tree = ROOT.TTree("tree", "tree")

    px = array("d", [0])

    py = array("d", [0])

    pz = array("d", [0])

    pi = array("i", [0])

    tree.Branch("x", px, "x/D")

    tree.Branch("y", py, "y/D")

    tree.Branch("z", pz, "z/D")

    tree.Branch("i", pi, "i/I")

    for i in range(100):

        px[0] = ROOT.gRandom.Gaus(0, 3)

        py[0] = ROOT.gRandom.Uniform() * 30 - 15

        pz[0] = ROOT.gRandom.Gaus(0, 5)

        pi[0] = i % 3

        tree.Fill()


    return tree


# Import multiple TH1 into a RooDataHist

# ----------------------------------------------------------


# Create thee ROOT ROOT.TH1 histograms

hh_1 = makeTH1("hh1", 0, 3)

hh_2 = makeTH1("hh2", -3, 1)

hh_3 = makeTH1("hh3", +3, 4)


# Declare observable x

x = ROOT.RooRealVar("x", "x", -10, 10)


# Create category observable c that serves as index for the ROOT histograms

c = ROOT.RooCategory("c", "c")

c.defineType("SampleA")

c.defineType("SampleB")

c.defineType("SampleC")


# Create a binned dataset that imports contents of all ROOT.TH1 mapped by

# index category c

dh = ROOT.RooDataHist("dh", "dh", [x], Index=c, Import={"SampleA": hh_1, "SampleB": hh_2, "SampleC": hh_3})

dh.Print()


dh2 = ROOT.RooDataHist("dh", "dh", [x], Index=c, Import={"SampleA": hh_1, "SampleB": hh_2, "SampleC": hh_3})

dh2.Print()


# Importing a ROOT TTree into a RooDataSet with cuts

# --------------------------------------------------------------------


tree = makeTTree()


# Define observables y,z

y = ROOT.RooRealVar("y", "y", -10, 10)

z = ROOT.RooRealVar("z", "z", -10, 10)


# Import only observables (y,z)

ds = ROOT.RooDataSet("ds", "ds", {x, y}, Import=tree)

ds.Print()


# Import observables (x,y,z) but only event for which (y+z<0) is ROOT.True

# Import observables (x,y,z) but only event for which (y+z<0) is ROOT.True

ds2 = ROOT.RooDataSet("ds2", "ds2", {x, y, z}, Import=tree, Cut="y+z<0")

ds2.Print()


# Importing integer ROOT TTree branches

# ---------------------------------------------------------------


# Import integer tree branch as ROOT.RooRealVar

i = ROOT.RooRealVar("i", "i", 0, 5)

ds3 = ROOT.RooDataSet("ds3", "ds3", {i, x}, Import=tree)

ds3.Print()


# Define category i

icat = ROOT.RooCategory("i", "i", {"State0": 0, "State1": 1})


# Import integer tree branch as ROOT.RooCategory (only events with i==0 and i==1

# will be imported as those are the only defined states)

ds4 = ROOT.RooDataSet("ds4", "ds4", {icat, x}, Import=tree)

ds4.Print()


# Import multiple RooDataSets into a RooDataSet

# ----------------------------------------------------------------------------------------


# Create three ROOT.RooDataSets in (y,z)

dsA = ds2.reduce({x, y}, "z<-5")

dsB = ds2.reduce({x, y}, "abs(z)<5")

dsC = ds2.reduce({x, y}, "z>5")


# Create a dataset that imports contents of all the above datasets mapped

# by index category c

dsABC = ROOT.RooDataSet("dsABC", "dsABC", {x, y}, Index=c, Import={"SampleA": dsA, "SampleB": dsB, "SampleC": dsC})


dsABC.Print()