R: Determine Duplicate Elements

duplicated2 {gdata} | R Documentation

## Determine Duplicate Elements

### Description

`duplicated2()` determines which elements of a vector or data frame are duplicates, and returns a logical vector indicating which elements (rows) are duplicates.

### Usage

    duplicated2(x, bothWays=TRUE, ...)

### Arguments

`x` | a vector or a data frame or an array or `NULL`.
`bothWays` | if `TRUE` (the default), duplication should be considered from both sides. For more information see the argument `fromLast` to the function `duplicated`.
`...` | further arguments passed down to `duplicated()` and its methods.

### Details

The standard `duplicated` function (in `package:base`) only returns `TRUE` for the second and following copies of each duplicated value (second-to-last and earlier when `fromLast=TRUE`). This function returns all duplicated elementes, including the first (last) value.

When `bothWays` is `FALSE`, `duplicated2()` defaults to a `duplicated` call. When `bothWays` is `TRUE`, the following call is being executed: `duplicated(x, ...) | duplicated(x, fromLast=TRUE, ...)`

### Value

For a vector input, a logical vector of the same length as `x`. For a data frame, a logical vector with one element for each row. For a matrix or array, and when `MARGIN = 0`, a logical array with the same dimensions and dimnames.

For more details see `duplicated`.

### Author(s)

Liviu Andronic

### See Also

`duplicated`, `unique`

### Examples

      data(iris)
      iris[duplicated(iris), ]                 # 2nd duplicated value
      iris[duplicated(iris, fromLast=TRUE), ]  # 1st duplicated value
      iris[duplicated2(iris), ]                # both duplicated values

[Package gdata version 2.18.0 Index]