duplicated               package:base               R Documentation

Determine Duplicate Elements

Description:

     Determines which elements of a vector of data frame are duplicates
     of elements with smaller subscripts, and returns a logical vector
     indicating which elements (rows) are duplicates.

Usage:

     duplicated(x, incomparables = FALSE)

Arguments:

       x: an atomic vector or a data fram.e

incomparables: a vector of values that cannot be compared. Currently,
          `FALSE' is the only possible value, meaning that all values
          can be compared.

Details:

     This is a generic function with methods for vectors and data
     frames. The data frame method works by pasting together a
     character representation of the rows separated by `\r', so may be
     imperfect if the data frame has characters with embedded carriage
     returns or columns which do not reliably map to characters.

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)]))

     data(iris)
     stopifnot(duplicated(iris)[143] == TRUE)

