This method function extracts the covariate(s) associated with
object
.
USAGE:
getCovariate(object, form, data)
REQUIRED ARGUMENTS:
object
an object inheriting from class
corStruct
representing a correlation structure.
OPTIONAL ARGUMENTS:
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.
data
an optional data frame in which to evaluate the variables
defined in
form, in case
object is not initialized and
the covariate needs to be evaluated.
VALUE:
when the correlation structure does not include a grouping factor, the
returned value will be a vector or a matrix with the covariate(s)
associated with
object. If a grouping factor is present, the
returned value will be a list of vectors or matrices with the
covariate(s) corresponding to each grouping level.