permute: Permutation Generation
In lmPerm: Permutation Tests for Linear Models

Description Usage Arguments Details Value Note Author(s) References

Generates permutations a pair at a time.

1	permute(N=4,K=1,initialize=0)

`N`	The number of elements in the permutation vector. The elements are numbered 1:N
`K`	The number of exchange pairs to be returned at each access
`initialize`	Set to 1 to initialize. Set to 0 for additional pairs.

On first call, set initialize to 1. On subsequent accesses, initialize should be 0. The function returns at most K exchange pairs at each access. The function should be repeatedly called until result is false.

The function returns a list.

`result`	Returns false when the last permutation has been generated or a failure has occurred. Returns true for success and at most K new pairs in vec.
`N`	The input parameter
`K`	The input parameter
`vec`	A 2*K vector of element numbers to be exchanged – permutations may be obtained by successively applying these pairs.
`initialize`	Always returns 1
`count`	The number of pairs in vec. It may be less than K for the final set.

This is the minimum time and effort routine. It is used for Exact permutation calculations. The present function is a wrapper for the C code and may be useful for other purposes. The code follows Reingole and Nievergelt (1977).

Bob Wheeler rwheeler@echip.com