With a simple combination of mutate_if and fct_explicit_na, you can replace all NAs in all factors with “Missing”:

If some of the words/symbols appear in white font, see the example here: Gist: factor_NA_levels.R

dplyr reference: http://dplyr.tidyverse.org/reference/index.html

forcats reference: http://dplyr.tidyverse.org/reference/index.html