duplicated

R Base 3.6.2

duplicated() determines which elements of a vector or data frame are duplicates of elements with smaller subscripts, and returns a logical vector indicating which elements (rows) are duplicates. anyDuplicated(.) is a “generalized” more efficient shortcut for any(duplicated(.)).

Syntax

duplicated(x, incomparables = FALSE, &#8230;)<p></p><p># S3 method for default
duplicated(x, incomparables = FALSE,
           fromLast = FALSE, nmax = NA, &#8230;)</p><p># S3 method for array
duplicated(x, incomparables = FALSE, MARGIN = 1,
           fromLast = FALSE, &#8230;)</p><p>anyDuplicated(x, incomparables = FALSE, &#8230;)
# S3 method for default
anyDuplicated(x, incomparables = FALSE,
           fromLast = FALSE, &#8230;)
# S3 method for array
anyDuplicated(x, incomparables = FALSE,
           MARGIN = 1, fromLast = FALSE, &#8230;)</p>

Arguments

Parameter	Description
`x`	a vector or a data frame or an array or NULL.
`incomparables`	a vector of values that cannot be compared. FALSE is a special value, meaning that all values can be compared, and may be the only value accepted for methods other than the default. It will be coerced internally to the same type as x.
`fromLast`	logical indicating if duplication should be considered from the reverse side, i.e., the last (or rightmost) of identical elements would correspond to duplicated = FALSE.
`nmax`	the maximum number of unique items expected (greater than one).
`…`	arguments for particular methods.
`MARGIN`	the array margin to be held fixed: see apply, and note that MARGIN = 0 may be useful.

Return Value

duplicated(): 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. anyDuplicated(): an integer or real vector of length one with value the 1-based index of the first duplicate if any, otherwise 0.

Details

These are generic functions with methods for vectors (including lists), data frames and arrays (including matrices). For the default methods, and whenever there are equivalent method definitions for duplicated and anyDuplicated, anyDuplicated(x, ...) is a “generalized” shortcut for any(duplicated(x, ...)), in the sense that it returns the index i of the first duplicated entry x[i] if there is one, and 0 otherwise. Their behaviours may be different when at least one of duplicated and anyDuplicated has a relevant method. duplicated(x, fromLast = TRUE) is equivalent to but faster than rev(duplicated(rev(x))). The array method calculates for each element of the sub-array specified by MARGIN if the remaining dimensions are identical to those for an earlier (or later, when fromLast = TRUE) eleme

Examples

Example

# NOT RUN {
x <- c(9:20, 1:5, 3:7, 0:8)
## extract unique elements
(xu <- x[!duplicated(x)])
## similar, same elements but different order:
(xu2 <- x[!duplicated(x, fromLast = TRUE)])

## xu == unique(x) but unique(x) is more efficient
stopifnot(identical(xu,  unique(x)),
          identical(xu2, unique(x, fromLast = TRUE)))

duplicated(iris)[140:143]

duplicated(iris3, MARGIN = c(1, 3))
anyDuplicated(iris) ## 143
# }
# NOT RUN {
anyDuplicated(x)
anyDuplicated(x, fromLast = TRUE)
# }