R: Dimensions of a corStruct Object

Dimensions of a corStruct Object

Dim(object, groups)

`object`	an object inheriting from class `corStruct`, representing a correlation structure.
`groups`	an optional factor defining the grouping of the observations; observations within a group are correlated and observations in different groups are uncorrelated.

if groups is missing, it returns the Dim attribute of object; otherwise, calculates the dimensions associated with the grouping factor.

a list with components:

`N`	length of `groups`
`M`	number of groups
`maxLen`	maximum number of observations in a group
`sumLenSq`	sum of the squares of the number of observations per group
`len`	an integer vector with the number of observations per group
`start`	an integer vector with the starting position for the observations in each group, beginning from zero

Jose Pinheiro and Douglas Bates

library(lme)
data(Orthodont)
Dim(corAR1(), getGroups(Orthodont))