permutations {arrangements}

Permutations generator

Description

This function generates all the permutations of selecting k items from n items. The results are in lexicographical order.

Usage

permutations(x = NULL, k = NULL, n = NULL, v = NULL, freq = NULL,
  replace = FALSE, layout = NULL, nitem = -1L, skip = NULL,
  index = NULL, nsample = NULL, drop = NULL)

Arguments

x

an integer or a vector, will be treated as n if integer; otherwise, will be treated as v. Should not be specified together with n and v.

k

an integer, the number of items drawn, defaults to n if freq is NULL else sum(freq)

n

an integer, the total number of items, its value may be implicitly deduced from length(v) or length(freq)

v

a vector to be drawn, defaults to 1:n.

freq

an integer vector of item repeat frequencies

replace

an logical to draw items with replacement

layout

if "row", "column" or "list" is specified, the returned value would be a "row-major" matrix, a "column-major" matrix or a list respectively

nitem

number of permutations required, usually used with skip

skip

the number of permutations skipped

index

a vector of indices of the desired permutations

nsample

sampling random permutations

drop

vectorize a matrix or unlist a list

See Also

ipermutations for iterating permutations and npermutations to calculate number of permutations

Examples

permutations(3)
permutations(LETTERS[1:3])

# choose 2 from 4
permutations(4, 2)
permutations(LETTERS[1:3], k = 2)

# multiset with frequencies c(2, 3)
permutations(k = 3, freq = c(2, 3))

# with replacement
permutations(4, 2, replace = TRUE)

# column major
permutations(3, layout = "column")
permutations(4, 2, layout = "column")

# list output
permutations(3, layout = "list")
permutations(4, 2, layout = "list")

# specifc range of permutations
permutations(4, 2, nitem = 2, skip = 3)

# specific permutations
permutations(4, 2, index = c(3, 5))

# random permutations
permutations(4, 2, nsample = 3)

# zero sized permutations
dim(permutations(0))
dim(permutations(5, 0))
dim(permutations(5, 6))
dim(permutations(0, 0))
dim(permutations(0, 1))