Replace NA in a series of variables by a factor level

Question

This is my data, and I want to replace NA with "No". I can replace missing values one by one. However, I need to replace NAs in s_1:s_4 in the code. Just as a reminder, all of the variables are factor levels.

id  x   s_0 s_1 s_2 s_3
1   5   75  A   4   110
2   9   36  NA  NA  921
3   11  13  B   7   769
4   11  34  C   2   912
5   11  NA  C   NA  835
6   13  39  NA  4   NA
7   14  45  B   4   577
8   19  42  D   6   NA
9   20  4   NA  7   577
10  13  28  NA  3   573 

Answer 1

If these are already existing factors, you can use forcats::fct_na_value_to_level():

library(dplyr)
library(forcats)

# Make sample data vars factors
dat <- dat %>%
  mutate(across(starts_with("s_"), as.factor))

# Add 'No' as factor level
dat %>%
  mutate(across(starts_with("s_"), ~ fct_na_value_to_level(.x, "No")))

# A tibble: 10 x 6
      id     x s_0   s_1   s_2   s_3  
   <dbl> <dbl> <fct> <fct> <fct> <fct>
 1     1     5 75    A     4     110  
 2     2     9 36    No    No    921  
 3     3    11 13    B     7     769  
 4     4    11 34    C     2     912  
 5     5    11 No    C     No    835  
 6     6    13 39    No    4     No   
 7     7    14 45    B     4     577  
 8     8    19 42    D     6     No   
 9     9    20 4     No    7     577  
10    10    13 28    No    3     573