Time until next occurence of value in pandas dataframe

Question

I am trying to find the time (in days) until next occurrence of each specific value. For example, say I have the data below:

    column1   created_at
0   A         2018-09-03
1   B         2018-09-07
2   B         2018-09-08
3   A         2018-09-09
4   B         2018-09-12

The goal is to get time difference for each value in column1 chronologically. At row 3 column1 value is A and its creation date is 2018-09-09. The last creation before that for A is 6 days ago.
Trying to get this:

    column1   created_at  time_diff
0   A         2018-09-03   NaN
1   B         2018-09-07   NaN
2   B         2018-09-08   1
3   A         2018-09-09   6
4   B         2018-09-12   4

Asked By: sakalansaka

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Source

Answer 1

Assuming this is the dataframe df

df['created_at'] = pd.to_datetime(df['created_at']) 
df['time_diff'] = df.groupby('column1')['created_at'].diff().dt.days

First row converts is date time, you can skip this if you want.
Second row gives you what you want.

Tick this answer if this solves your problem.

Answered By: DJKarma

Time until next occurence of value in pandas dataframe

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