unique {base}

R Documentation

Extract Unique Elements

Description

unique returns a vector or data frame like x but with duplicate elements removed. If an element is equal to one with a smaller index, it is removed.

Usage

unique(x, incomparables = FALSE)

Arguments

x	an atomic vector or a data frame.
incomparables	a vector of values that cannot be compared. Currently, FALSE is the only possible value, meaning that all values can be compared.

See Also

duplicated which gives the indices of duplicated elements.

Examples

unique(c(3:5, 11:8, 8 + 0:5))
length(unique(sample(100, 100, replace=TRUE)))
## approximately 100(1 - 1/e) = 63.21
my.unique <- function(x) x[!duplicated(x)]
for(i in 1:4)
 { x <- rpois(100, pi); stopifnot(unique(x) == my.unique(x)) }

data(iris)
unique(iris)
stopifnot(dim(unique(iris)) == c(149, 5))

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