gnm (version 1.1-5)

Symm: 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 = ":")

Value

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

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.

Author

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))