R: Draw a Random Permutation Vector with Exchangeability...

rperm {sna} | R Documentation

## Draw a Random Permutation Vector with Exchangeability Constraints

### Description

Draws a random permutation on `1:length(exchange.list)` such that no two elements whose corresponding `exchange.list` values are different are interchanged.

### Usage

    rperm(exchange.list)

### Arguments

`exchange.list` | A vector such that the permutation vector may exchange the ith and jth positions iff `exchange.list[i]==exchange.list[j]`

### Details

`rperm` draws random permutation vectors given the constraints of exchangeability described above. Thus, `rperm(c(0,0,0,0))` returns a random permutation of four elements in which all exchanges are allowed, while `rperm(c(1,1,"a","a")` (or similar) returns a random permutation of four elements in which only the first/second and third/fourth elements may be exchanged. This turns out to be quite useful for searching permutation spaces with exchangeability constraints (e.g., for structural distance estimation).

### Value

A random permutation vector satisfying the given constraints

### Author(s)

Carter T. Butts buttsc@uci.edu

### See Also

`rmperm`

### Examples

    rperm(c(0,0,0,0))  #All elements may be exchanged
    rperm(c(0,0,0,1))  #Fix the fourth element
    rperm(c(0,0,1,1))  #Allow {1,2} and {3,4} to be swapped
    rperm(c("a",4,"x",2))  #Fix all elements (the identity permutation)

[Package sna version 2.6 Index]