

   duplicated {base}                            R Documentation

   DDeetteerrmmiinnee DDuupplliiccaattee EElleemmeennttss

   DDeessccrriippttiioonn::

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

   UUssaaggee::

        duplicated(x)

   AArrgguummeennttss::

          x: an atomic vector

   SSeeee AAllssoo::

        `unique'.

   EExxaammpplleess::

        x <- c(9:20, 1:5, 3:7, 0:8)
        ## extract unique elements
        (xu <- x[!duplicated(x)])
        all(xu == unique(x)) # TRUE, but unique(x) is more efficient
        all(0:20  == sort(x[!duplicated(x)]))

