states_map <- map_data('state')
str(states_map)
Error: Package `maps` required for `map_data`.
Please install and try again.
Traceback:

1. map_data("state")
2. try_require("maps", "map_data")
3. stop("Package `", package, "` required for `", fun, "`.\n", "Please install and try again.", 
 .     call. = FALSE)