use purrr::map_dfc to update all cells in a data.frame

purrr_map_dfc_example.R

# replace all insances of '.' in all columns without changing anything else.
dt <- data.frame(
  a=sample(LETTERS, 10),
  b=sample(c('.', 1, 2, 3), 10, replace=T),
  c=sample(c('.', 'rick', 'morty', 'summer'), 10, replace=T))
 
 # print the data.frame
 dt
 
 # use purrr::map_dfc to loop through the columns of the data.frame
 dt %>% 
   purrr::map_dfc(
     function(x) str_replace(x, '^\\.$', replacement=NA_character_))