df003_profiles.py

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## \file
## \ingroup tutorial_dataframe
## \notebook -draw
## Use TProfiles with RDataFrame.
##
## This tutorial illustrates how to use TProfiles in combination with the
## RDataFrame. See the documentation of TProfile and TProfile2D to better
## understand the analogy of this code with the example one.
##
## \macro_code
## \macro_image
##
## \date February 2017
## \author Danilo Piparo (CERN)
 
import ROOT
 
# A simple helper function to fill a test tree: this makes the example
# stand-alone.
def fill_tree(treeName, fileName):
    d = ROOT.RDataFrame(25000)
    d.Define("px", "gRandom->Gaus()")\
     .Define("py", "gRandom->Gaus()")\
     .Define("pz", "sqrt(px * px + py * py)")\
     .Snapshot(treeName, fileName)
 
# We prepare an input tree to run on
fileName = "df003_profiles_py.root"
treeName = "myTree"
fill_tree(treeName, fileName)
 
# We read the tree from the file and create a RDataFrame.
columns = ROOT.vector('string')()
columns.push_back("px")
columns.push_back("py")
columns.push_back("pz")
d = ROOT.RDataFrame(treeName, fileName, columns)
 
# Create the profiles
hprof1d = d.Profile1D(("hprof1d", "Profile of pz versus px", 64, -4, 4))
hprof2d = d.Profile2D(("hprof2d", "Profile of pz versus px and py", 40, -4, 4, 40, -4, 4, 0, 20))
 
# And Draw
c1 = ROOT.TCanvas("c1", "Profile histogram example", 200, 10, 700, 500)
hprof1d.Draw()
c1.SaveAs("df003_c1.png")
 
c2 = ROOT.TCanvas("c2", "Profile2D histogram example", 200, 10, 700, 500)
hprof2d.Draw()
c2.SaveAs("df003_c2.png")
 
print("Saved figures to df003_*.png")