“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

Here's an attempt using make.unique to account for duplicates:

dupdiff <- function(x,y) x[-match(
  make.unique(as.character(y)),
  make.unique(as.character(x)),
  nomatch=0
)]

Testing:

dupdiff(x,y)
#[1] 1 3 8
dupdiff(x,z)
#[1] 1 5 7
dupdiff(x, c(5, 7))
#[1] 1 3 3 8
dupdiff(x, c(5, 7, 9))
#[1] 1 3 3 8