r4ds 7 summarize
The last key verb is summarise(). It collapses a data frame to a single row:
summarise(flights, delay = mean(dep_delay, na.rm = TRUE))
summarise() is not terribly useful unless we pair it with group_by(). by_day <- group_by(flights, year, month, day)
summarise(by_day, delay = mean(dep_delay, na.rm = TRUE))Follow me!
