1.2

nycflights13::flights
filter(flights,arr_delay>120)
filter(flights, dest=="IAH"|dest=="HOU")
filter(flights, carrier %in% c("AA", "DL", "UA"))
filter(flights, month >= 7, month <= 9)
filter(flights, arr_delay > 120, dep_delay <= 0)
filter(flights, dep_delay >= 60, dep_delay - arr_delay > 30)
summary(flights$dep_time)
arrange(flights, desc(is.na(dep_time)), dep_time)
select(flights, dep_time, dep_delay, arr_time, arr_delay)
select(flights, "dep_time", "dep_delay", "arr_time", "arr_delay")
select(flights, 4, 6, 7, 9)
select(flights, year, month, day, year, year)
flights %>%
  filter(!is.na(tailnum)) %>%
  mutate(on_time = !is.na(arr_time) & (arr_delay <= 0)) %>%
  group_by(tailnum) %>%
  summarise(on_time = mean(on_time), n = n()) %>%
  filter(min_rank(on_time) == 1)