Combining i, j, and by (II)
As you did in the last chapter, you will combine the i
, j
, and by
arguments, but this time modify the existing data.table
by reference in j
.
This exercise is part of the course
Data Manipulation with data.table in R
Exercise instructions
For all rows where duration
is greater than 600, group batrips
by start_station
and end_station
to add a new column (mean_duration
) by reference which calculates the mean duration of all trips.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# Add the mean_duration column
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