Cumulative sum that resets based on the year

Asked Feb 10 '21 at 17:29

Active Feb 10 '21 at 17:29

Viewed 207 times

I have a pandas df:

pd.DataFrame({'team': ['ARI','ARI','ARI','BAL','BAL','BAL','BUF','BUF','BUF'],
          'year': [2019, 2019, 2020, 2019, 2019, 2020, 2019, 2019, 2020],
          'week': [16,17,1,16,17,1,16,17,1],
          'hits': [1, 3, 2, 2, 2, 5, 3, 3, 2]})

I want to overwrite the "hits" column to a cumulative sum, but the cumsum must reset every "year". Expected output:

pd.DataFrame({'team': ['ARI','ARI','ARI','BAL','BAL','BAL','BUF','BUF','BUF'],
          'year': [2019, 2019, 2020, 2019, 2019, 2020, 2019, 2019, 2020],
          'week': [16,17,1,16,17,1,16,17,1],
          'cumsum_hits': [1,4,2,2,4,5,3,6,2]})

asked Feb 10 '21 at 17:29

Michael Mathews Jr.

1

`df.groupby(['team','year'])['hits'].cumsum()` – Quang Hoang Feb 10 '21 at 17:30
The week column needs to be included like in my expected output. – Michael Mathews Jr. Feb 10 '21 at 17:31
1

Assign that to a new column in your dataframe: `df['cumsum_hits'] = ...`? – Quang Hoang Feb 10 '21 at 17:32

Cumulative sum that resets based on the year

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