getGroups.corStruct {nlme}

Extract corStruct Groups

Description

This method function extracts the grouping factor associated with object, if any is present.

Usage

## S3 method for class 'corStruct'
getGroups(object, form, level, data, sep)

Arguments

object

an object inheriting from class corStruct representing a correlation structure.

form

this argument is included to make the method function compatible with the generic. It will be assigned the value of formula(object) and should not be modified.

level

this argument is included to make the method function compatible with the generic and is not used.

data

an optional data frame in which to evaluate the variables defined in form, in case object is not initialized and the grouping factor needs to be evaluated.

sep

character, the separator to use between group levels when multiple levels are collapsed. The default is '/'.

Value

if a grouping factor is present in the correlation structure represented by object, the function returns the corresponding factor vector; else the function returns NULL.

Author(s)

José Pinheiro and Douglas Bates [e-mail]

See Also

getGroups

Examples

cs1 <- corAR1(form = ~ 1 | Subject)
getGroups(cs1, data = Orthodont)