How to replace NA values with another value in factors in R?
You can use this function : 

forcats::fct_explicit_na

library(forcats) 
fct_explicit_na(DF$col, na_level = "None")


Usage

It can be used within the mutate function and piped to edit DF directly: 

library(tidyverse) # for tidy data packages, automatically loads dplyr
library(magrittr) # for piping
DF %&lt;&gt;% mutate(cols = fct_explicit_na(col, na_level = "None"))


Note that "col" needs to be a factor for this to work.