# combinations: Enumerate the Combinations of the Elements of a Vector In OBsMD: Objective Bayesian Model Discrimination in Follow-Up Designs

## Description

`combinations` enumerates the possible combinations of a specified size from the elements of a vector.

## Usage

 `1` ```combinations(n, r, v=1:n, set=TRUE, repeats.allowed=FALSE) ```

## Arguments

 `n` Size of the source vector `r` Size of the target vectors `v` Source vector. Defaults to `1:n` `set` Logical flag indicating whether duplicates should be removed from the source vector `v`. Defaults to `TRUE`. `repeats.allowed` Logical flag indicating whether the constructed vectors may include duplicated values. Defaults to `FALSE`.

## Details

Caution: The number of combinations increases rapidly with `n` and `r`!.

To use values of `n` above about 45, you will need to increase R's recursion limit. See the `expression` argument to the `options` command for details on how to do this.

## Value

Returns a matrix where each row contains a vector of length `r`.

## Author(s)

Original versions by Bill Venables Bill.Venables@cmis.csiro.au. Extended to handle `repeats.allowed` by Gregory R. Warnes greg@warnes.net.

## References

Venables, Bill. "Programmers Note", R-News, Vol 1/1, Jan. 2001. https://cran.r-project.org/doc/Rnews

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10``` ```combinations(3,2,letters[1:3]) combinations(3,2,c(1:3),repeats=TRUE) combinations(6,3,1:6,repeats=TRUE) # To use large 'n', you need to change the default recusion limit options(expressions=1e5) cmat <- combinations(100,2) dim(cmat) # 4950 by 2 ```

OBsMD documentation built on July 1, 2020, 10:22 p.m.