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) 

REQUIRED ARGUMENTS:

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

OPTIONAL ARGUMENTS:

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:

,

EXAMPLES:

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