duplicated {base} | R Documentation |
Determines which elements of a vector are duplicates of elements with smaller subscripts, and returns a logical vector indicating which elements are duplicates.
duplicated(x, incomparables = FALSE)
x |
an atomic vector |
incomparables |
For S compatibility. Other values are not yet implemented in R.
x <- c(9:20, 1:5, 3:7, 0:8) ## extract unique elements (xu <- x[!duplicated(x)]) stopifnot(xu == unique(x), # but unique(x) is more efficient 0:20 == sort(x[!duplicated(x)]))