DougKruger DougKruger - 1 year ago 133
Python Question

How to join two dataframes where datetime column is in between each other

Given two dataframes

df_1
and
df_2
, how to join them such that datetime column
df_1
is in between
start
and
end
in dataframe
df_2
:

print df_1

timestamp A B
0 2016-05-14 10:54:33 0.020228 0.026572
1 2016-05-14 10:54:34 0.057780 0.175499
2 2016-05-14 10:54:35 0.098808 0.620986
3 2016-05-14 10:54:36 0.158789 1.014819
4 2016-05-14 10:54:39 0.038129 2.384590


print df_2

start end event
0 2016-05-14 10:54:31 2016-05-14 10:54:33 E1
1 2016-05-14 10:54:34 2016-05-14 10:54:37 E2
2 2016-05-14 10:54:38 2016-05-14 10:54:42 E3


Get corresponding
event
where
df1.timestamp
is between
df_2.start
and
df2.end


timestamp A B event
0 2016-05-14 10:54:33 0.020228 0.026572 E1
1 2016-05-14 10:54:34 0.057780 0.175499 E2
2 2016-05-14 10:54:35 0.098808 0.620986 E2
3 2016-05-14 10:54:36 0.158789 1.014819 E2
4 2016-05-14 10:54:39 0.038129 2.384590 E3

Answer Source

One simple solution is create interval index from start and end setting closed = both then use get_loc to get the event i.e (Hope all the date times are in timestamps dtype )

df_2.index = pd.IntervalIndex.from_arrays(df_2['start'],df_2['end'],closed='both')
df_1['event'] = df_1['timestamp'].apply(lambda x : df_2.iloc[df_2.index.get_loc(x)]['event'])

Output :

            timestamp         A         B event
0 2016-05-14 10:54:33  0.020228  0.026572    E1
1 2016-05-14 10:54:34  0.057780  0.175499    E2
2 2016-05-14 10:54:35  0.098808  0.620986    E2
3 2016-05-14 10:54:36  0.158789  1.014819    E2
4 2016-05-14 10:54:39  0.038129  2.384590    E3
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