Identifying elements of a vector which is not found in another comparable vector in R

Question

I want to know the exact elements of a vector not found in the vector. For instance, consider the following vectors:

veca <- c("ab", "cd", "ef", "gh", "ij", "kl")
vecb <- c("ab", "ef", "ij", "kl")

From this, cd and gh are in veca but not in vecb. How can one identify these elements in R? Thanks!

Answer 1

We could define a custom function like an opposite intersect function using setdiff:

learned here:

outersect <- function(x, y) {
  sort(c(setdiff(x, y),
         setdiff(y, x)))
}

outersect(veca, vecb)

output:

[1] "cd" "gh"

Another possible solution is:

not_in_vecb <- veca[!veca %in% vecb]

[1] "cd" "gh"