If present, the grouping factor associated to the correlation
structure for the linear model represented by object is extracted.
Usage
getGroups(object)
Arguments
object
an object inheriting from class gls, representing
a generalized least squares fitted linear model.
Value
if the linear model represented by object incorporates a
correlation structure and the corresponding corStruct object
has a grouping factor, a vector with the group values is returned;
else, NULL is returned.