Variance Design Object

DESCRIPTION:

Objects of class "varDesign" specifying a variance structure for geeDesign.

GENERATION:

These objects are generated by function varDesign .

METHODS:

There are no special methods associated with class "varDesign" .

VALUE:

Objects of class "varDesign" are lists with the following components:
type
a character string to specify a variance structure.
terms
A data frame in which there is a one-to-one correspondence between rows and terms with scale in the variance formula having the following variables:
fixed

A logical variable indicating whether or not the scale is fixed for the corresponding term.

scale
The fixed value of the scale if the scale is fixed for the corresponding term, and otherwise a default starting value for the scale for that term.
weight
For weighted terms, the name of the weight associated with the corresponging term, otherwise NA .
level
The level of the grouping variable associated with each term ( type = "glm.hetero" only).

group
A character string giving the name of a factor variable that serves as an indicator for heterogeneous groups ( type = "glm.hetero" only).
weight
A character string giving the name of a variable to be used for weighting heterogeneous groups ( type = "glm.hetero" only).
model
A formula describing the variance model.

DETAILS:

The object is mainly used to specify the variance argument in the geeDesign function. It is also a component of a "geeDesign" object.

SEE ALSO:

, .