varDesign(type="glm.scale", fixed, scale, weights, levels, group)
type = "glm.1",
type = "glm.disp" or
type = "glm.scale", no other
arguments to
varDesign need be specified
when terms are unweighted.
If
type = "glm.hetero",
arguments
levels
and
group must also be specified.
Options for the
type argument are:
weight variable
must be specified in
terms argument to
varDesign
.
hetero argument to
varDesign
must be specified.
type="glm.fixed",
type="glm.mixed",
type="glm.hetero",
type="poly")
A logical variable or vector with
having a one-to-one correspondence with the variance terms
indicating whether or not the scale is fixed.
type="glm.fixed",
type="glm.mixed",
type="glm.hetero",
type="poly")
A numeric vector
having a one-to-one correspondence with the variance terms
giving the fixed value of the scale if
the scale is fixed, and otherwise
either
NA or
a default starting value for the scale.
If NA is given (no starting value) a moment estimate is computed using
the residuals computed from the initial coefficient estimates (typically
computed from the
S-PLUS function
glm).
NA. A weight is required for each term
if
type = "glm.mixed".
When
type = "glm.hetero",
only one weight is allowed.
The
weights argument
can be omitted in cases where there are no weights.
type="glm.hetero",
not used for other variance types)
A vector of character strings
having a one-to-one correspondence with the variance terms
giving the associated level of the grouping variable.
type="glm.hetero",
not used for other variance types)
A character string giving the name of a factor variable
that serves as an indicator for heterogeneous groups.
"varDesign" is returned.
See
varDesign.object for details.
The output of
varDesign is used mainly
for the
variance argument
in
geeDesign.
It checks for consistency of the other arguments with
type
,
creates a data frame describing the variance terms,
and gives a formula for the variance model.
For
type = "poly", there must be a row
for terms order 0 up to the degree of the polynomial even if they
vanish in the polynomial formula.
Vanishing terms are specified by setting
fixed = T
and
scale = 0.
When weights or a grouping variable
are specified,
the variables named
in those arguments must be either in the search path
or in the data associated
when used in a call to
geeDesign.
It is recommended that users review
varDesign
objects before using them in calls to
geeDesign.
varDesign(type="glm.1")
varDesign(type="glm.scale")
varDesign(type="glm.fixed", fixed = T, scale = .5)
varDesign(type="glm.mixed", fixed = c(F,F,T), scale = c(1,1,1),
weights = c("u","v","w"))
varDesign(type="poly", fixed = c(F,F,F,F), scale = c(1,1,1,1))
varDesign(type="poly", fixed = c(T,T,T,F), scale = c(0,1,0,-2),
weights = c(NA, "x", NA, "z"))
varDesign(type="glm.hetero", fixed = c(T,F,F), scale = c(1,1,1),
levels = c("alpha", "beta", "gamma"), group = "x", weights = "w")