Creating a Cumulative Frequency Column in a Dataframe Python

Question

I am trying to create a new column named 'Cumulative Frequency' in a data frame where it consists of all the previous frequencies to the frequency for the current row as shown here.

What is the way to do this?

Answer 1

You want cumsum:

df['Cumulative Frequency'] = df['Frequency'].cumsum()

Example:

In [23]:
df = pd.DataFrame({'Frequency':np.arange(10)})
df

Out[23]:
   Frequency
0          0
1          1
2          2
3          3
4          4
5          5
6          6
7          7
8          8
9          9

In [24]:
df['Cumulative Frequency'] = df['Frequency'].cumsum()
df

Out[24]:
   Frequency  Cumulative Frequency
0          0                     0
1          1                     1
2          2                     3
3          3                     6
4          4                    10
5          5                    15
6          6                    21
7          7                    28
8          8                    36
9          9                    45