| unique {base} | R Documentation |
unique returns a vector, data frame or array like x
but with duplicate elements removed.
unique(x, incomparables = FALSE, ...) ## S3 method for class 'array': unique(x, incomparables = FALSE, MARGIN = 1, ...)
x |
a vector or a data frame or an array or NULL. |
incomparables |
a vector of values that cannot be compared.
Currently, FALSE is the only possible value, meaning that all
values can be compared. |
... |
arguments for particular methods. |
MARGIN |
the array margin to be held fixed: a single integer. |
This is a generic function with methods for vectors, data frames and arrays (including matrices).
The array method calculates for each element of the dimension
specified by MARGIN if the remaining dimensions are identical
to those for an earlier element (in row-major order). This would most
commonly be used to find unique rows (the default) or columns
(with MARGIN = 2).
An object of the same type of x. but if
an element is equal to one with a smaller index, it is removed.
Dimensions of arrays are not dropped.
Using this for lists is potentially slow, especially if the elements
are not atomic vectors (see vector) or differ only
in their attributes. In the worst case it is O(n^2).
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
duplicated which gives the indices of duplicated
elements.
unique(c(3:5, 11:8, 8 + 0:5)) length(unique(sample(100, 100, replace=TRUE))) ## approximately 100(1 - 1/e) = 63.21 unique(iris)