filter()
slice()
arrange()
select()
summarize()
sum(x > 10) 和 mean(y == 0)
group_by()
dplyr::all_equal()
janitor::compare_df_cols()
vetr::alike()
diffdf::diffdf()
readr
readxl
pivot_longer()
pivot_wider()
separate()
untie()
unite()
chop()
unchop()
uncount()
map()
imap()
WDIsearch()
WDI
freq
descr()
clean_names
tabyl
get_dupes
remove_
round_half_up
excel_numeric_to_date
top_levels
row_to_names
after_join()
frq()
flat_table()
rec()
purrr tutorial : https://jennybc.github.io/purrr-tutorial/