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temp = df.groupby('date')['t'].cumsum().rename('t_cumulative')
df = df.merge(temp, on='date_time', how='outer')
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solved Calculate cumulative intraday measures that reset every day in pandas
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temp = df.groupby('date')['t'].cumsum().rename('t_cumulative')
df = df.merge(temp, on='date_time', how='outer')
[ad_2]
solved Calculate cumulative intraday measures that reset every day in pandas