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.
Questo esercizio fa parte del corso
Data Manipulation with data.table in R
Istruzioni dell'esercizio
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.
Esercizio pratico interattivo
Prova a risolvere questo esercizio completando il codice di esempio.
# Add the mean_duration column
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