Just remembered that I have a shortcut on my work machine to open a shuffled image gallery (via #nsxiv) of the best photos of my dearly departed furson.
The map() function applies a function across vectors, lists, or data frames efficiently. Syntax: map(.x, .f, ...) where .x is data, .f is function, ... for extra args. Examples: square vector elements via ~.x^2, get means of column across list of data frames with ~mean(.x$y), apply custom functions to rows/cols like df$z <- map_dbl(df, add_cols).