These functions determine which characters the decimal mark and big mark should be that are used in plotting. They base the determination on getOption("OutDec"), which is also what base::format() uses.
Details
If the option "dec_mark" is set, that value will be used for dec_mark() if it is either a comma or a full stop.
At default, big_mark() returns a full stop if dec_mark() returns a comma, and a space otherwise. If the option "big_mark" is set, that value will be used if it is either a comma (",") or a full stop (".") or a space (" ") or an empty character ("").
Examples
# at default, this follows `getOption("OutDec")`:
dec_mark()
#> [1] "."
# and big_mark() returns a space if dec_mark() returns ".":
big_mark()
#> [1] " "
# you you can set options to alter behaviour:
options(dec_mark = ",", big_mark = ".")
dec_mark()
#> [1] ","
big_mark()
#> [1] "."
options(dec_mark = ",", big_mark = NULL)
dec_mark()
#> [1] ","
big_mark()
#> [1] "."
options(big_mark = ",")
dec_mark()
#> [1] ","
big_mark()
#> [1] ","
# clean up
options(dec_mark = NULL, big_mark = NULL)