Fill a column with one of four date columns based on another R

I have a DF with 5 columns like so;

A  B  Date1 Date2 Date3 Date4
1       x     NA    NA    NA
2      NA     y     NA    NA
3      NA    NA     z     NA  
4      NA    NA    NA     f

I want to use the dplyr package and the case_when() function to state something like this

df <- df %>%
    mutate(B = case_when(
     A == 1 ~ B == Date1,
     A == 2 ~ B == Date2,
     A == 3 ~ B == Date3,
     A == 4 ~ B == Date4))

Essentially based on the value of A I would like to fill B with one of 4 date coloumns.
A is of class character, B and the Date are all class Date.

Problem is when I apply this to the dataframe it simply doesn’t work. It returns NAs and changes the class of B to boolean. I am using R version 4.1.2. Any help is appreciated.

>Solution :

The other answers are superior, but if you must use your current code for the actual application, the corrected version is:

df %>%
  mutate(B = case_when(
    A == 1 ~ Date1,
    A == 2 ~ Date2,
    A == 3 ~ Date3,
    A == 4 ~ Date4))

Output:

# A B Date1 Date2 Date3 Date4
# 1 x     x  <NA>  <NA>  <NA>
# 2 y  <NA>     y  <NA>  <NA>
# 3 z  <NA>  <NA>     z  <NA>
# 4 f  <NA>  <NA>  <NA>     f