Using .SD (I)

.SD together with .SDcols is an incredibly powerful feature that makes computing on multiple columns so much easier.

.SD is a special symbol which stands for Subset of Data
.SDcols holds the columns that should be included in .SD

This exercise is part of the course

Data Manipulation with data.table in R

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Exercise instructions

For each month, find the row corresponding to the shortest trip (by using which.min() on duration).
The result should contain the month, start_station, end_station, start_date, end_date, and duration columns.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

relevant_cols <- c("start_station", "end_station", 
                   "start_date", "end_date", "duration")

# Find the row corresponding to the shortest trip per month
shortest <- batrips[, ___, 
                    by = month(start_date), 
                    .SDcols = ___]
shortest

Edit and Run Code