formula(object)
object
| an object inheriting from class code{pdMat}, representing a positive definite matrix. |
pdMat
object, in which the column and row names are specified.object
has a formula
attribute, its value is
returned, else NULL
is returned.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.pdMat
library(lme) pd1 <- pdSymm(~Sex*age) formula(pd1)