Add NA to the column (that already has NA and values) based on a condition in another column in R

Question

I have a data frame like this

a b    f
0 S NA
0 A 0.88
1 A 0.85
0 A 0.98
1 A 1.01
1 S NA
1 B 1.03

and would like to add NA to column 'f', based on the value of 'a' (if a == 1); also not affecting the NAs that are already in the column'f'

so it would look like this

   a b    f
1: 0 S NA
2: 0 A 0.88
3: 1 A NA
4: 0 A 0.98
5: 1 A NA
6: 1 S NA
7: 1 B NA

any suggestions is greatly appreciated Thanks m

Answer 1

You can also use the is.na<- replacement function.

is.na(df$f) <- df$a == 1

Here's an example with your data.

within(df, is.na(f) <- a == 1)
#   a b    f
# 1 0 S   NA
# 2 0 A 0.88
# 3 1 A   NA
# 4 0 A 0.98
# 5 1 A   NA
# 6 1 S   NA
# 7 1 B   NA

Answer 2

Just do

df$f[df$a == 1] <- NA