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.
Latihan ini adalah bagian dari kursus
Data Manipulation with data.table in R
Petunjuk latihan
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.
Latihan interaktif praktis
Cobalah latihan ini dengan menyelesaikan kode contoh berikut.
# Add the mean_duration column
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