next_subset: Select Next Subset
| next_subset | R Documentation |
Select Next Subset
Description
Select next subset of size k from a set of size n.
Usage
next_subset(a, n, k)
Arguments
a |
a numeric vector (integers) |
n |
an integer: the size of the set to choose from |
k |
an integer: the subset size |
Details
Given a subset a of size k taken from a set of size n, compute the next subset by alphabetical order.
Uses algorithm NEXKSB of Nijenhuis and Wilf (1975).
Value
a numeric vector (the next subset) or NULL
(when there is no next subset)
Author(s)
Enrico Schumann
References
Nijenhuis, A. and Wilf, H. S. (1975) Combinatorial Algorithms for Computers and Calculators. Academic Press.
See Also
choose computes the number of combinations
combn creates all combinations
expand.grid
Examples
n <- 4
k <- 2
t(combn(n, k))
## [,1] [,2]
## [1,] 1 2
## [2,] 1 3
## [3,] 1 4
## [4,] 2 3
## [5,] 2 4
## [6,] 3 4
a <- 1:k
print(a)
while (!is.null(a))
print(a <- next_subset(a, n = n, k = k))
## [1] 1 2
## [1] 1 3
## [1] 1 4
## [1] 2 3
## [1] 2 4
## [1] 3 4
