df017_vecOpsHEP.py
## \file
## \ingroup tutorial_dataframe
## \notebook -draw
## This tutorial shows how VecOps can be used to slim down the programming
## model typically adopted in HEP for analysis.
##
## \macro_code
## \macro_image
##
## \date March 2018
## \author Danilo Piparo, Andre Vieira Silva
import ROOT
filename = ROOT.gROOT.GetTutorialDir().Data() + "/dataframe/df017_vecOpsHEP.root"
treename = "myDataset"
def WithPyROOT(filename):
from math import sqrt
f = ROOT.TFile(filename)
h = ROOT.TH1F("pt", "pt", 16, 0, 4)
for event in f.myDataset:
for E, px, py in zip(event.E, event.px, event.py):
if (E > 100):
h.Fill(sqrt(px*px + py*py))
h.DrawCopy()
def WithRDataFrameVecOpsJit(treename, filename):
f = ROOT.ROOT.RDataFrame(treename, filename)
h = f.Define("good_pt", "sqrt(px*px + py*py)[E>100]")\
.Histo1D(("pt", "pt", 16, 0, 4), "good_pt")
h.DrawCopy()
## We plot twice the same quantity, the key is to look into the implementation
## of the functions above
c = ROOT.TCanvas()
c.Divide(2,1)
c.cd(1)
WithPyROOT(filename)
c.cd(2)
WithRDataFrameVecOpsJit(treename, filename)