R: Symmetric Interaction of Factors

Symm {gnm} | R Documentation

## Symmetric Interaction of Factors

### Description

`Symm` codes the symmetric interaction of factors having the same set of levels, for use in regression models of symmetry or quasi-symmetry.

### Usage

    Symm(..., separator = ":")

### Arguments

`...` | one or more factors.
`separator` | a character string of length 1 or more, to be used in naming the levels of the resulting interaction factor.

### Value

A factor whose levels index the symmetric interaction of all factors supplied as input.

### Author(s)

David Firth and Heather Turner

### See Also

`Diag`

### Examples

    # square table
    rowfac <- gl(4, 4, 16)
    colfac <- gl(4, 1, 16)
    symm4by4 <- Symm(rowfac, colfac)
    matrix(symm4by4, 4, 4)

    # 3 x 3 x 3 table
    ind <- expand.grid(A = 1:3, B = 1:3, C = 1:3)
    symm3cubed <- with(ind, Symm(A, B, C))
    array(symm3cubed, c(3, 3, 3))

[Package gnm version 1.1-2 Index]