duplicated {base}R Documentation

Determine Duplicate Elements

Description

Determines which elements of a vector are duplicates of elements with smaller subscripts, and returns a logical vector indicating which elements are duplicates.

Usage

duplicated(x, incomparables = FALSE)

Arguments

x an atomic vector
incomparables a vector of values that cannot be compared. Currently, FALSE is the only possible value, meaning that all values can be compared.

See Also

unique.

Examples

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)]))