Compositions iterator

This function returns a Compositions iterator for iterating compositions of an non-negative integer n into k parts or parts of any sizes. The iterator allows users to fetch the next partition(s) via the getnext() method.

Compositions

icompositions(n, k = NULL, descending = FALSE, skip = NULL)

Arguments

n	an non-negative integer to be partitioned
k	number of parts
descending	an logical to use reversed lexicographical order
skip	the number of compositions skipped

Format

An object of class R6ClassGenerator of length 25.

Details

The Compositions class can be initialized by using the convenient wrapper icompositions or

Compositions$new(n, k = NULL, descending = 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

See also

compositions for generating all compositions and ncompositions to calculate number of compositions

Examples

ipart <- icompositions(4)
ipart$getnext()
#> [1] 1 1 1 1
ipart$getnext(2)
#>      [,1] [,2] [,3] [,4]
#> [1,]    1    1    2    0
#> [2,]    1    2    1    0
ipart$getnext(layout = "column", drop = FALSE)
#>      [,1]
#> [1,]    1
#> [2,]    3
#> [3,]    0
#> [4,]    0
# collect remaining compositions
ipart$collect()
#>      [,1] [,2] [,3] [,4]
#> [1,]    2    1    1    0
#> [2,]    2    2    0    0
#> [3,]    3    1    0    0
#> [4,]    4    0    0    0

library(foreach)
foreach(x = icompositions(6, 2), .combine=c) %do% {
  prod(x)
}
#> [1] 5 8 9 8 5