Counting number of occurrences on the whole Pandas DataFrame

Question

My dataset has this structure

A = [A1, A2, A3, A4]
B = [B1, B2, B3]
C = [C1, C2, C3, C4, C5]

I want to count the occurrences of all variables in my dataset, such as:

A1    3
A2    2
A3    1
...
C4    4
C5    5

I have tried

df.groupby(df.columns[0]).A.count()

but it only works column by column, is there any way to count occurrences for the whole dataset at once? Thank you.

Answer 1

You can use stack the value_counts

df.stack().value_counts()
Out[1298]: 
4    2
3    2
2    2
5    1
1    1
dtype: int64

Data input

df=pd.DataFrame({'A':[1,2,3,4],'B':[2,3,4,5]})

Answer 2

pd.value_counts(df.values.ravel())

Answer 3

You can use apply with count on axis = 1

>>> df=pd.DataFrame({'A':[1,2,3,4],'B':[2,3,4,5]})
>>> df.apply(pd.value_counts).count(axis=1)

Outputs

1    1
2    2
3    2
4    2
5    1
dtype: int64