df017_vecOpsHEP.py File Reference

Namespaces
namespace	df017_vecOpsHEP

Detailed Description

Use RVecs to plot the transverse momentum of selected particles.

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", "With PyROOT", 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", "With RDataFrame and RVec", 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)
c.SaveAs("df017_vecOpsHEP.png")
 
print("Saved figure to df017_vecOpsHEP.png")

Date

March 2018

Authors

Danilo Piparo (CERN), Andre Vieira Silva

Definition in file df017_vecOpsHEP.py.