Why is there no mode method for groupby objects?

[connerxyz]

There is mean, max, median, min and mad yet no mode for groupby objects. Is there a good reason? What if I add and issue pull-request?

[sinhrks]

related to #11562. Nice to discuss how the output should be.

[jreback]

yes, closing as a duplicate of that issue.

The crus is that mode is not a reducer (like sum, mean) and such, nor is it a straight filter, like nth, or tail. Its like .value_counts which we don't directly support either via groupby

you can do this:

In [6]: df = DataFrame({'A' : [1,2,1,2], 'B' : [1,1,1,1]})

In [7]: df
Out[7]: 
   A  B
0  1  1
1  2  1
2  1  1
3  2  1

In [8]: df.groupby('A').B.value_counts()
Out[8]: 
A  B
1  1    2
2  1    2
Name: B, dtype: int64

In [9]: df.groupby('A').B.apply(lambda x: x.mode())
Out[9]: 
A   
1  0    1
2  0    1
Name: B, dtype: int64