Filling in a new column based on a condition in a data frame

Question

I want to add a new column in my data frame so that for each row if LOC == 1 then V is equal to the value given for V1; if LOC==

Answer 1

If LOC only contains 1 or 2 then this will work

 df$V <- ifelse(df$LOC == 1, df$V1, df$V2)