explain/log outcome of each operation

[ocramz]

e.g. as in https://elbersb.com/public/posts/tidylog100/

filtered <- filter(mtcars, cyl == 4)
#> filter: removed 21 rows (66%), 11 rows remaining

joined <- left_join(nycflights13::flights, nycflights13::weather,
    by = c("year", "month", "day", "origin", "hour", "time_hour"))
#> left_join: added 9 columns (temp, dewp, humid, wind_dir, wind_speed, …)
#>            > rows only in x     1,556
#>            > rows only in y  (  6,737)
#>            > matched rows     335,220
#>            >                 =========
#>            > rows total       336,776