c()
filter()
arrange()
select()
mutate()
if_else()
rename()
drop_na()
sample_n()
sample_frac()
distinct()
n_distinct()
slice()
summarise()
group_by()
summarise_all()
str_trim()
str_pad()
str_detect()
str_subset()
str_which()
str_extract()
str_match()
str_replace()
str_split()
duration
period
interval
We have finished a nice book.