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:
,
.