df006_ranges¶

Use Range to limit the amount of data processed.

This tutorial shows how to express the concept of ranges when working with the RDataFrame.

Author: Danilo Piparo (CERN)
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, March 27, 2023 at 09:45 AM.

In [1]:

import ROOT

def fill_tree(treeName, fileName):
    df = ROOT.RDataFrame(100)
    df.Define("b1", "(int) rdfentry_")\
      .Define("b2", "(float) rdfentry_ * rdfentry_").Snapshot(treeName, fileName)

Welcome to JupyROOT 6.29/01

We prepare an input tree to run on

In [2]:

fileName = "df006_ranges_py.root"
treeName = "myTree"

fill_tree(treeName, fileName)

We read the tree from the file and create a RDataFrame.

In [3]:

d = ROOT.RDataFrame(treeName, fileName)

Usage of ranges¶

Now we'll count some entries using ranges

In [4]:

c_all = d.Count()

This is how you can express a range of the first 30 entries

In [5]:

d_0_30 = d.Range(30) 
c_0_30 = d_0_30.Count()

This is how you pick all entries from 15 onwards

In [6]:

d_15_end = d.Range(15, 0)
c_15_end = d_15_end.Count()

We can use a stride too, in this case we pick an event every 3 entries

In [7]:

d_15_end_3 = d.Range(15, 0, 3)
c_15_end_3 = d_15_end_3.Count()

The Range here acts first on the (whole) RDataFrame graph: Not only actions (like Count) but also filters and new columns can be added to it.

In [8]:

d_0_50 = d.Range(50)
c_0_50_odd_b1 = d_0_50.Filter("1 == b1 % 2").Count()

An important thing to notice is that the counts of a filter are relative to the number of entries a filter "sees". Therefore, if a Range depends on a filter, the Range will act on the entries passing the filter only.

In [9]:

c_0_3_after_even_b1 = d.Filter("0 == b1 % 2").Range(0, 3).Count()

Ok, time to wrap up: let's print all counts!

In [10]:

print("Usage of ranges:")
print(" - All entries:", c_all.GetValue())
print(" - Entries from 0 to 30:", c_0_30.GetValue())
print(" - Entries from 15 onwards:", c_15_end.GetValue())
print(" - Entries from 15 onwards in steps of 3:", c_15_end_3.GetValue())
print(" - Entries from 0 to 50, odd only:", c_0_50_odd_b1.GetValue())
print(" - First three entries of all even entries:", c_0_3_after_even_b1.GetValue())

Usage of ranges:
 - All entries: 100
 - Entries from 0 to 30: 30
 - Entries from 15 onwards: 85
 - Entries from 15 onwards in steps of 3: 29
 - Entries from 0 to 50, odd only: 25
 - First three entries of all even entries: 3