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
library(nlme) pd1 <- pdSymm(~Sex*age) formula(pd1)