R: All Combinations of k Elements from Vector v

combs {caTools} | R Documentation

## All Combinations of k Elements from Vector v

### Description

Finds all unordered combinations of `k` elements from vector `v`.

### Usage

    combs(v,k)

### Arguments

`v` | Any numeric vector
`k` | Number of elements to choose from vector `v`. Integer smaller or equal than length of `v`.

### Value

`combs(v,k)` (where `v` has length `n`) creates a matrix with n!/((n-k)! k!) (`n` choose `k`) rows and `k` columns containing all possible combinations of `n` elements taken `k` at a time.

### Author(s)

Jarek Tuszynski (SAIC) jaroslaw.w.tuszynski@saic.com

### See Also

I discovered recently that R packages already have two functions with similar capabilities: `combinations` from gTools package and Also similar to Matlab's `nchoosek` function (http://www.mathworks.com/access/helpdesk/help/techdoc/ref/nchoosek.html)

### Examples

      combs(2:5, 3) # display examples
      combs(c("cats", "dogs", "mice"), 2)

      a = combs(1:4, 2)
      b = matrix( c(1,1,1,2,2,3,2,3,4,3,4,4), 6, 2)
      stopifnot(a==b)

[Package caTools version 1.17.1.1 Index]