Rank Combinations and Permutations

Generate the rank (lexicographically) of combinations/permutations. These functions are the complement to comboSample and permuteSample. See the examples below.
GMP support allows for exploration of combinations/permutations of vectors with many elements.

Usage

comboRank(..., v, repetition = FALSE, freqs = NULL)
permuteRank(..., v, repetition = FALSE, freqs = NULL)

Arguments

...: vectors or matrices to be ranked.
v: Source vector. If v is a positive integer, it will be converted to the sequence 1:v. If v is a negative integer, it will be converted to the sequence v:-1. All atomic types are supported (See is.atomic).
repetition: Logical value indicating whether combinations/permutations should be with or without repetition. The default is FALSE.
freqs: A vector of frequencies used for producing all combinations/permutations of a multiset of v. Each element of freqs represents how many times each element of the source vector, v, is repeated. It is analogous to the times argument in rep. The default value is NULL.

Details

These algorithms rely on efficiently ranking the \(n^{th}\) lexicographical combination/permutation.

Value

A vector of class integer, numeric, or bigz determined by the total number of combinations/permutations

References

Lexicographical order ranking/unranking

Author

Joseph Wood

Note

v must be supplied.

Examples

mySamp = comboSample(30, 8, TRUE, n = 5, seed = 10, namedSample = TRUE)
myRank = comboRank(mySamp, v = 30, repetition = TRUE)
all.equal(as.integer(rownames(mySamp)), myRank)
#> [1] TRUE