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Determine Repeated Elements

Source: R/repeated.r
repeated.Rd

Return a logical vector, indices, or the values of repeated elements in a vector.

Usage

repeated(x, ...)

# S3 method for class 'array'
repeated(x, MARGIN = 1L, ...)

whichRepeated(x, ...)

# S3 method for class 'array'
whichRepeated(x, MARGIN = 1L, ...)

repeats(x, ...)

# S3 method for class 'array'
repeats(x, MARGIN = 1L, ...)

non.unique(x, ...)

Arguments

x

a vector, a data frame, an array, or NULL.

...

additional arguments passed to methods.

MARGIN

the array margin to be held fixed: see apply, and note that MARGIN = 0 may be useful.

Value

repeated(): 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.

whichRepeated(): For a vector input, an integer vector giving the indices of the repeated values. For a data frame, an integer vector giving the indices of the repeated rows. For a matrix or array, an integer vector giving the indices of the repeated elements across the margin specified.

repeats() and its alias non.unique(): an object of the same type as x, containing the repeated values (vector input), rows (data frame input), or elements across the margin (matrix/array input).

Details

The repeated functions determine which elements of a vector or data frame are duplicates of elements with smaller subscripts. They are very similar in functionality to duplicated but instead mark all duplicates (not just those after the first/last occurrence), and do not have an incomparables argument.

These are generic functions with methods for vectors (including lists and expressions), data frames and arrays (including matrices).

The array method calculates for each element of the sub-array specified by MARGIN if the dimensions are identical to those for an earlier or later element (in row-major order). This would most commonly be used to find repeated rows (the default) or columns (with MARGIN = 2). Note that MARGIN = 0 returns an array of the same dimensionality attributes as x.

non.unique() is an alias for repeats().

See also

duplicated and unique.

Examples

# Repeated values in a vector
x <- c(1, 2, 3, 2, 1)

repeated(x)
#> [1]  TRUE  TRUE FALSE  TRUE  TRUE
whichRepeated(x)
#> [1] 1 2 4 5
repeats(x)
#> [1] 1 2 2 1

# Repeated rows in a data frame
df <- data.frame(
  x = c(1, 2, 1),
  y = c("a", "b", "a")
)

repeated(df)
#> [1]  TRUE FALSE  TRUE
repeats(df)
#>   x y
#> 1 1 a
#> 3 1 a

# Repeated rows/columns in a matrix
m <- cbind(
  c(1, 2),
  c(3, 4),
  c(1, 2)
)

repeated(m)
#> [1] FALSE FALSE
repeated(m, MARGIN = 2)
#> [1]  TRUE FALSE  TRUE
repeats(m, MARGIN = 2)
#>      [,1] [,2]
#> [1,]    1    1
#> [2,]    2    2

# non.unique() is an alias for repeats()
identical(repeats(x), non.unique(x))
#> [1] TRUE