{dplyr}
keep specified columns
{base}
load R packages
{dplyr}
create or modify data columns
{stringr}
replace all matched patterns in a string
{tibble}
create tibble
{readr}
parse date
{base}
create vector of numbers, characters, etc.
{readr}
parse a character vector to numbers
{utils}
return first rows of matrix, data frame, etc.
The end!