glsStruct list
are initialized.initialize(object, data, control)glsStruct,
representing a list of linear model components, such as
corStruct and varFunc objects.formula(object).gls. Defaults to list(singular.ok = FALSE, qrTol =
.Machine$single.eps), implying that linear dependencies are not
glsStruct object similar to object, but with
initialized model components.gls, initialize.corStruct ,
initialize.varFunc