arrangements: icombinations – R documentation

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icombinations

Combinations iterator

Description

This function returns a Combinations iterator for iterating combinations of k items from n items. The iterator allows users to fetch the next combination(s) via the getnext() method.

Usage

Combinations

icombinations(x = NULL, k = NULL, n = NULL, v = NULL,
  freq = NULL, replace = FALSE, skip = 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
`skip`	the number of combinations skipped

Format

An object of class R6ClassGenerator of length 25.

Details

The Combinations class can be initialized by using the convenient wrapper icombinations or

Combinations$new(n, k, v = NULL, freq = NULL, replace = FALSE)

getnext(d = 1L, layout = NULL, drop = NULL)
collect(layout = "row")
reset()

d: number of fetched arrangements
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
drop: vectorize a matrix or unlist a list

Examples

icomb <- icombinations(5, 2)
icomb$getnext()
icomb$getnext(2)
icomb$getnext(layout = "column", drop = FALSE)
# collect remaining combinations
icomb$collect()

library(foreach)
foreach(x = icombinations(5, 2), .combine=c) %do% {
  sum(x)
}

arrangements

Fast Generators and Iterators for Permutations, Combinations, Integer Partitions and Compositions

v1.1.9

MIT + file LICENSE

Authors

Randy Lai [aut, cre]

Initial release

2020-09-12