fac.vcmat {dae}

forms the variance matrix for the variance component of a (generalized) factor

Description

Form the variance matrix for a (generalized) factor whose effects for its different levels are independently and identically distributed, with their variance given by the variance component; elements of the matrix will equal either zero or sigma2 and displays compound symmetry.

Usage

fac.vcmat(factor, sigma2)

Arguments

factor

The (generalized) factor for which the variance matrix is required.

sigma2

The variance component, being the of the random effects for the factor.

Details

The method is: a) form the n x n summation or relationship matrix whose elements are equal to zero except for those elements whose corresponding elements in the following two n x n matrices are equal: 1) each row contains the numeric values corresponding to the observed levels of the factor, and 2) each column contains the numeric values corresponding to the observed levels of the factor, b) multiply the summation matrix by sigma2.

Value

An n x n matrix, where n is the length of the factor.

Author(s)

Chris Brien

See Also

fac.ar1mat, fac.meanop, fac.sumop in package dae.

Examples

## set up a two-level factor and a three-level factor, both of length 12
A <- factor(rep(1:2, each=6))
B <- factor(rep(1:3, each=2, times=2))

## create a 12 x 12 ar1 matrix corrresponding to B
vc.B <- fac.vcmat(B, 2)