“Set Difference” between two vectors with duplicate values

Question

I have 3 vectors

x <- c(1,3,5,7,3,8)
y <- c(3,5,7)
z <- c(3,3,8)

I want to find the elements of x that are not in

Answer 1

match with a little for-loop does work:

> f(x, y)
[1] 1 3 8
> f(x, z)
[1] 1 5 7

Code

f <- function(s, r) {
    for(i in 1:length(s)){
        j <- match(s[i], r)
        if(!is.na(j)) {
            s[i] <- NA
            r[j] <- NA
        } 
    }
    print(s[complete.cases(s)])
}