I have a set of IDs and Timestamps, and want to calculate the "total time elapsed per ID" by getting the difference of the oldest / earliest timestamps, grouped by ID.
Data
id timestamp
1 2018-02-01 03:00:00
1 2018-02-01 03:01:00
2 2018-02-02 10:03:00
2 2018-02-02 10:04:00
2 2018-02-02 11:05:00
Expected Result
( I want the delta converted to minutes )
id delta
1 1
2 62
I have a for loop, but it's very slow (10+ min for 1M+ rows). I was wondering if this was achievable via pandas functions?
# gb returns a DataFrameGroupedBy object, grouped by ID
gb = df.groupby(['id'])
# Create the resulting df
cycletime = pd.DataFrame(columns=['id','timeDeltaMin'])
def calculate_delta():
for id, groupdf in gb:
time = groupdf.timestamp
# returns timestamp rows for the current id
time_delta = time.max() - time.min()
# convert Timedelta object to minutes
time_delta = time_delta / pd.Timedelta(minutes=1)
# insert result to cycletime df
cycletime.loc[-1] = [id,time_delta]
cycletime.index += 1
Thinking of trying next:
- Multiprocessing
First ensure datetimes are OK:
df.timestamp = pd.to_datetime(df.timestamp)
Now find the number of minutes in the difference between the maximum and minimum for each id:
import numpy as np
>>> (df.timestamp.groupby(df.id).max() - df.timestamp.groupby(df.id).min()) / np.timedelta64(1, 'm')
id
1 1.0
2 62.0
Name: timestamp, dtype: float64
You can sort by id
and tiemstamp
, then groupby id
and then find the difference between min and max timestamp per group.
df['timestamp'] = pd.to_datetime(df['timestamp'])
result = df.sort_values(['id']).groupby('id')['timestamp'].agg(['min', 'max'])
result['diff'] = (result['max']-result['min']) / np.timedelta64(1, 'm')
result.reset_index()[['id', 'diff']]
Output:
id diff
0 1 1.0
1 2 62.0
Another one:
import pandas as pd
import numpy as np
import datetime
ids = [1,1,2,2,2]
times = ['2018-02-01 03:00:00','2018-02-01 03:01:00','2018-02-02
10:03:00','2018-02-02 10:04:00','2018-02-02 11:05:00']
df = pd.DataFrame({'id':ids,'timestamp':pd.to_datetime(pd.Series(times))})
df.set_index('id', inplace=True)
print(df.groupby(level=0).diff().sum(level=0)['timestamp'].dt.seconds/60)
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