R: Change levels inside a function

Question

I have a data.frame and I want to change levels of a factor variable so I do this:

> df1 <- data.frame(id = 1:5, fact1 = factor(letters[1:5]))
> head(df         


        

Answer 1

you need to return the full object x rather than just the result of your assignment (which is the string missing).

changeLevel1 <- function(x){
   levels(x)[which(levels(x) == 'a')] <- 'missing'
   return (x)
}