Check if column data exists in column and return value of the another column in R

I want to check if values from column B exist in column A, and if yes and equal with the value in that row, create another column D, getting the value from column C (for the A on that row).

This is what I have, but it’s not working as it should as it is setting the value of D by just checking if the value exists in column A and not comparing them.

  ifelse(df$B %in% df$A, df$C , NA)

>Solution :

You could also do:

transform(df1, D = setNames(C,A)[B])

  A B  C  D
1 a f 12 55
2 b a 23 12
3 c b 33 23
4 d c  1 33
5 e e 11 11
6 f d 55  1