[FIXED] Pandas, rolling max that ignores NaN

Issue

I want to calculate the max value in the past 3 rolling rows, ignoring NaN if I see them. I assumed that skipna would do that, but it doesn't. How can I ignore NaN, and also what is skipna supposed to do?

In this code

import pandas as pd

df = pd.DataFrame({'sales': [25, 20, 14]})
df['max'] = df['sales'].rolling(3).max(skipna=True)
print(df)

The last column is

   sales   max
0     25   NaN
1     20   NaN
2     14  25.0

But I want it to be

   sales   max
0     25  25.0
1     20  25.0
2     14  25.0

Solution

You can also use Series.bfill with your command:

df['max'] = df['sales'].rolling(3).max().bfill()

Output:

   sales   max
0     25  25.0
1     20  25.0
2     14  25.0

Answered By - Mayank Porwal