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Reference Guide
df006_ranges.py
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1## \file
2## \ingroup tutorial_dataframe
3## \notebook -nodraw
4## This tutorial shows how to express the concept of ranges when working with the RDataFrame.
5##
6## \macro_code
7## \macro_output
8##
9## \date March 2017
10## \author Danilo Piparo
11
12import ROOT
13
14def fill_tree(treeName, fileName):
15 df = ROOT.RDataFrame(100)
16 df.Define("b1", "(int) rdfentry_")\
17 .Define("b2", "(float) rdfentry_ * rdfentry_").Snapshot(treeName, fileName)
18
19
20# We prepare an input tree to run on
21fileName = "df006_ranges_py.root"
22treeName = "myTree"
23
24fill_tree(treeName, fileName)
25
26# We read the tree from the file and create a RDataFrame.
27d = ROOT.RDataFrame(treeName, fileName)
28
29# ## Usage of ranges
30# Now we'll count some entries using ranges
31c_all = d.Count()
32
33# This is how you can express a range of the first 30 entries
34d_0_30 = d.Range(0, 30)
35c_0_30 = d_0_30.Count()
36
37# This is how you pick all entries from 15 onwards
38d_15_end = d.Range(15, 0)
39c_15_end = d_15_end.Count()
40
41# We can use a stride too, in this case we pick an event every 3
42d_15_end_3 = d.Range(15, 0, 3)
43c_15_end_3 = d_15_end_3.Count()
44
45# The Range is a 1st class citizen in the RDataFrame graph:
46# not only actions (like Count) but also filters and new columns can be added to it.
47d_0_50 = d.Range(0, 50)
48c_0_50_odd_b1 = d_0_50.Filter("1 == b1 % 2").Count()
49
50# An important thing to notice is that the counts of a filter are relative to the
51# number of entries a filter "sees". Therefore, if a Range depends on a filter,
52# the Range will act on the entries passing the filter only.
53c_0_3_after_even_b1 = d.Filter("0 == b1 % 2").Range(0, 3).Count()
54
55# Ok, time to wrap up: let's print all counts!
56print("Usage of ranges:")
57print(" - All entries:", c_all.GetValue())
58print(" - Entries from 0 to 30:", c_0_30.GetValue())
59print(" - Entries from 15 onwards:", c_15_end.GetValue())
60print(" - Entries from 15 onwards in steps of 3:", c_15_end_3.GetValue())
61print(" - Entries from 0 to 50, odd only:", c_0_50_odd_b1.GetValue())
62print(" - First three entries of all even entries:", c_0_3_after_even_b1.GetValue())
ROOT's RDataFrame offers a high level interface for analyses of data stored in TTrees,...
Definition: RDataFrame.hxx:42
Ta Range(0, 0, 1, 1)