CODEWITHSUNDEEP
pythonpandasdataframe
Logan
Logan

Reputation: 293

Python Pandas : How to get days difference from first date

Trying to find the date difference grouping by ID and using the first date by ID as the starting point.

Input

ID Date
1  1/1/2020
1  1/1/2020
1  1/5/2020
2  1/1/2020
2  1/3/2020
2  1/10/2020

Output

ID Date       DateDiff
1  1/1/2020   0
1  1/1/2020   0
1  1/5/2020   4
2  1/1/2020   0
2  1/3/2020   2
2  1/10/2020  9

Upvotes: 1

Views: 193

Answers (1)

Ben.T
Ben.T

Reputation: 29635

you can use groupby.transform and first.

df['DateDiff'] = pd.to_datetime(df['Date']) #to work with datetime object
df['DateDiff'] = (df['DateDiff']-
                  df['DateDiff'].groupby(df['ID']).transform('first')).dt.days

print(df)

   ID       Date  DateDiff
0   1   1/1/2020         0
1   1   1/1/2020         0
2   1   1/5/2020         4
3   2   1/1/2020         0
4   2   1/3/2020         2
5   2  1/10/2020         9

Upvotes: 3

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