plydata.helper_verbs.count¶
-
class
plydata.helper_verbs.
count
(*args, **kwargs)[source]¶ Count observations by group
count
is a convenient wrapper for summarise that will either call n or sum(n) depending on whether you’re tallying for the first time, or re-tallying. Similar totally
, but it does thegroup_by
for you.- Parameters
Examples
>>> import pandas as pd >>> from plydata import count, group_by, summarize >>> df = pd.DataFrame({ ... 'x': [1, 2, 3, 4, 5, 6], ... 'y': ['a', 'b', 'a', 'b', 'a', 'b'], ... 'w': [1, 2, 1, 2, 1, 2]})
Without groups it is one large group
>>> df >> count() n 0 6
Sum of the weights
>>> df >> count(weights='w') n 0 9
With groups
>>> df >> count('y') y n 0 a 3 1 b 3
With groups and weights
>>> df >> count('y', weights='w') y n 0 a 3 1 b 6
Applying the weights to a column
>>> df >> count('y', weights='x*w') y n 0 a 9 1 b 24
You can do that with
summarize
>>> df >> group_by('y') >> summarize(n='sum(x*w)') y n 0 a 9 1 b 24