nlme (version 3.1-1)

getGroupsFormula.gls: Extract gls Object Grouping Formula

Description

If present, the grouping formula associated with the correlation structure (corStruct) of object is returned either as a named list with a single one-sided formula, or a single one-sided formula, depending on the value of asList. If object does not include a correlation structure, or if the correlation structure does not include groups, NULL is returned.

Usage

getGroupsFormula(object, asList)

Arguments

object

an object inheriting from class gls, representing a generalized least squares fitted linear model.

asList

an optional logical value. If TRUE the returned value with be a list of formulas; else, if FALSE the returned value will be a one-sided formula. Defaults to FALSE.

Value

• if a correlation structure with groups is included in object, a one-sided formula, or a list with a single one-sided formula, with the corresponding grouping structure, else NULL.

See Also

corClasses, getGroups.gls

Examples

data(Ovary)
fm1 <- gls(follicles ~ sin(2*pi*Time) + cos(2*pi*Time), Ovary,
           correlation = corAR1(form = ~ 1 | Mare))
getGroupsFormula(fm1)