formula.pdMat {nlme} | R Documentation |
This method function extracts the formula associated with a
pdMat
object, in which the column and row names are specified.
formula(object)
object |
an object inheriting from class pdMat , representing
a positive definite matrix. |
if object
has a formula
attribute, its value is
returned, else NULL
is returned.
Because factors may be present in formula(object)
, the
pdMat
object needs to have access to a data frame where the
variables named in the formula can be evaluated, before it can resolve
its row and column names from the formula.
Jose Pinheiro and Douglas Bates
pd1 <- pdSymm(~Sex*age) formula(pd1)