df017_vecOpsHEP.py File Reference

Namespaces
namespace	df017_vecOpsHEP

Detailed Description

This tutorial shows how VecOps can be used to slim down the programming model typically adopted in HEP for analysis.

 
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.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)

Date

March 2018

Author

Danilo Piparo, Andre Vieira Silva

Definition in file df017_vecOpsHEP.py.