9 purrr

purrr tutorial : https://jennybc.github.io/purrr-tutorial/

9.2 Producing atomic vectors

9.4 group_

9.4.1 group_map、group_modify

group_map(), group_modify() and group_walk() are purrr-style functions that can be used to iterate on grouped tibbles.

This is similar to split() and then map():

9.4.2 group_split、group_keys、group_data

only grouping variables:

only rows: