Select a language for swirl's menus.
select_language(language = NULL, append_rprofile = FALSE)The language that swirl's menus will use.
This must be one of the following values: "chinese_simplified".
"english", "french", "german",
"korean", "spanish", or "turkish".
If NULL the user will be asked to choose a language
interactively. The default value is NULL.
If TRUE this command will append
options(swirl_language = [selected language]) to the end of your
Rprofile. The default value is FALSE.