npermutations: Number of permutations

In arrangements: Fast Generators and Iterators for Permutations, Combinations, Integer Partitions and Compositions

Description

Number of permutations

Usage

npermutations(x = NULL, k = NULL, n = NULL, v = NULL,
  freq = NULL, replace = FALSE, bigz = FALSE)

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
bigz	an logical to use gmp::bigz

See Also

permutations for generating all permutations and ipermutations for iterating permutations

Examples

npermutations(7)
npermutations(LETTERS[1:5])
npermutations(5, 2)
npermutations(LETTERS, k = 5)

# integer overflow
## Not run: npermutations(14, 10)
npermutations(14, 10, bigz = TRUE)

# number of permutations of `c("a", "b", "b")`
# they are `c("a", "b")`, `c("b", "b")` and `c("b", "b")`
npermutations(k = 2, freq = c(1, 2))

# zero sized partitions
npermutations(0)
npermutations(5, 0)
npermutations(5, 6)
npermutations(0, 1)
npermutations(0, 0)

Example output

[1] 5040
[1] 120
[1] 20
[1] 7893600
Big Integer ('bigz') :
[1] 3632428800
[1] 3
[1] 1
[1] 1
[1] 0
[1] 0
[1] 1

arrangements documentation built on Sept. 13, 2020, 5:20 p.m.