In addition to its plotting tools, Pandas also offers a convenient .value_counts() method that computes a histogram of non-null values to a Pandas Series:
Python
>>> import pandas as pd
>>> data = np.random.choice(np.arange(10), size=10000,
... p=np.linspace(1, 11, 10) / 60)
>>> s = pd.Series(data)
>>> s.value_counts()
9 1831
8 1624
7 1423
6 1323
5 1089
4 888
3 770
2 535
1 347
0 170
dtype: int64
>>> s.value_counts(normalize=True).head()
9 0.1831
8 0.1624
7 0.1423
6 0.1323
5 0.1089
dtype: float64
Elsewhere, pandas.cut() is a convenient way to bin values into arbitrary intervals. Let’s say you have some data on ages of individuals and want to bucket them sensibly:
Python
>>> ages = pd.Series(
... [1, 1, 3, 5, 8, 10, 12, 15, 18, 18, 19, 20, 25, 30, 40, 51, 52])
>>> bins = (0, 10, 13, 18, 21, np.inf) # The edges
>>> labels = ('child', 'preteen', 'teen', 'military_age', 'adult')
>>> groups = pd.cut(ages, bins=bins, labels=labels)
>>> groups.value_counts()
child 6
adult 5
teen 3
military_age 2
preteen 1
dtype: int64
>>> pd.concat((ages, groups), axis=1).rename(columns={0: 'age', 1: 'group'})
age group
0 1 child
1 1 child
2 3 child
3 5 child
4 8 child
5 10 child
6 12 preteen
7 15 teen
8 18 teen
9 18 teen
10 19 military_age
11 20 military_age
12 25 adult
13 30 adult
14 40 adult
15 51 adult
16 52 adult
What’s nice is that both of these operations ultimately utilize Cython code that makes them competitive on speed while maintaining their flexibility.