multic (version 0.4.3.1)

subsets: Choose Sets Of Size k From The n-Elements Of a Vector

Description

Return a matrix where each row is a set of size k chosen from the n elements in vector v. Optional to allow repeated elements.

Usage

subsets(n, k, v=1:n, allow.repeat=F)

Arguments

n

Length of element vector.

k

Number of elements chosen in the subsets.

v

Vector including elements from which to choose. If not specified, integers 1 to n are used.

allow.repeat

Logical, if (T)rue, include repeats of the same integer.

Value

Matrix with k columns and varying number of rows. Each row is the size=k subset of integers 1:n. If no repeats allowed, it will have nCk = n!/((n-k)!k!) rows. If repeats allowed, (n+k)!/((n-1)!k!) rows.

Side Effects

References

Venebles, W.N. and Ripley, B.D., "Statistics and Computing", New York: Springer-Verlag. 2000. 49+

Details

Optional to allow repeats in the subsets. Sets all sorted lowest element to highest. This function does almost the same as combinations(), but this function uses recursion, which allows it to work very fast. In using recursion, it runs into problems in the amount of data frames needed for the recursive calls. This limit is reached with an n near 20, and worse with a larger k.

See Also

combine

Examples

## Not run: 
# sets <- subsets(5, 3, v=6:10)
# sets.w.rep_subsets(5,3,v=6:10, allow.repeat=T)
#   ## sets has 10 rows and sets w/repeats has 35 rows.
# ## End(Not run)