Using Counter() in Python to build histogram?

Question

I saw on another question that I could use Counter() to count the number of occurrences in a set of strings. So if I have ['A','B','A','C','A','A'] I get Counter({'A':3,'B':1,'C':1}). But now, how can I use that information to build a histogram for example?

Answer 1

For your data it is probably better to use a barchart instead of a histogram. Check out this code:

from collections import Counter
import numpy as np
import matplotlib.pyplot as plt


labels, values = zip(*Counter(['A','B','A','C','A','A']).items())

indexes = np.arange(len(labels))
width = 1

plt.bar(indexes, values, width)
plt.xticks(indexes + width * 0.5, labels)
plt.show()

Result:

Answer 2

You can write some really concise code to do this using pandas:

In [24]: import numpy as np

In [25]: from pandas import Series

In [27]: sample = np.random.choice(['a', 'b'], size=10)

In [28]: s = Series(sample)

In [29]: s
Out[29]:
0    a
1    b
2    b
3    b
4    a
5    b
6    b
7    b
8    b
9    a
dtype: object

In [30]: vc = s.value_counts()

In [31]: vc
Out[31]:
b    7
a    3
dtype: int64

In [32]: vc = vc.sort_index()

In [33]: vc
Out[33]:
a    3
b    7
dtype: int64

In [34]: vc.plot(kind='bar')

Resulting in: