No, there isn't a built in function to do that, but you could easily code it yourself with
`%nin%` = Negate(`%in%`)
Or
`%!in%` = Negate(`%in%`)
See this thread and followup discussion: %in% operator - NOT IN
Also, it was pointed out the package Hmisc includes the operator %nin%, so if you're using it for your applications it's already there.
library(Hmisc)
"A" %nin% "B"
#[1] TRUE
"A" %nin% "A"
#FALSE
