R: Extracting Variables and Model Matrices for Generalized...
drgeeData
R Documentation
Extracting Variables and Model Matrices for Generalized Estimating equations
Description
Given a main model, an outcome nuisance model and an
exposure nuisance model drgeeData extracts the model
variables and matrices from a data.frame or an environment
object. It also performs some data cleaning and error checking.
The outcome as a variable or as a character string naming a variable in the
data argument. If it is not found in the data
argument, it will be searched for in the calling frame. If missing,
the outcome is assumed to be the response of oformula.
exposure
The exposure as a variable or as a character string naming a variable in the
data argument. If it is not found in the data
argument, it will be searched for in the calling frame. If missing,
the outcome is assumed to be the response of eformula.
oformula
An expression or formula for the outcome nuisance model. The outcome
is identified as the response in this formula.
eformula
An expression or formula for the exposure nuisance model. The
exposure is identified as the response in this formula.
iaformula
An expression or formula where the RHS should contain the variables
that "interact" (i.e. are supposed to be multiplied with) with the
exposure in the main model to create the terms associated with the
parameters of interest. "1" will always added. Default value is no
interactions, i.e. formula(~1).
olink
A character string naming the link function in the outcome nuisance
model. Have to be "identity", "log" or
"logit". Default is "identity".
elink
A character string naming the link function in the exposure nuisance
model. Have to be "identity", "log" or
"logit". Default is "identity". When
olink="logit" this is replaced by "logit".
data
A data frame or environment containing the variables in iaformula,
oformula and eformula. If missing, variables are
expected to be found in the calling frame.
estimation.method
A character string naming the desired estimation method. Choose
"o" for O-estimation,
"e" for E-estimation or
"dr" for DR-estimation. Default is "dr".
cond
A logical value indicating whether the nuisance models should have
cluster-specific intercepts. If cond=TRUE the design matrices
for the nuisance models do not have an intercept. Requires a
clusterid argument.
clusterid
A cluster-defining variable or a character string naming a cluster-defining variable in the
data argument. If it is not found in the data
argument, it will be searched for in the calling frame. If missing,
each observation will be considered to be a separate cluster. This
argument is required when cond = TRUE.
Details
drgeeData is called by drgee and gee to extract
data from a data.frame or environment
object. The data can then be used to for O-estimation, E-estimation or
DR-estimation. drgeeData uses
model.frame and model.matrix to remove incomplete
observations and to convert factors to dummy variables. It also
performs check the supplied data for errors or inconsistencies.
The class method summary.drgeeData produces strings for the
formulas with terms referring to the columns in the produced design
matrices.
Value
drgee.data returns an object of class drgeeData
containing
orig.order
The original order of the observations.
y
The outcome matrix.
a
The exposure matrix.
x
The matrix of of interactions defined in iaformula.
This matrix will always contain a column with 1's.
ax
The matrix of elementwise product(s) of a and
each column in x.
v
The matrix of terms in the outcome nuisance model.
z
The matrix of terms in the exposure nuisance model.
yx
The matrix of elementwise product(s) of y and each
column in x.
id
A factor defining clusters. For independent observations,
the number of levels equals the number of complete observations.
clustname
A string for the name of the cluster defining variable.
y.names
A string for the name of the outcome.
a.names
A string for the name of the exposure.
x.names
A string vector for the variable names in x.
ax.names
A string vector for the variable names in ax.
v.names
A string vector for the variable names in v.
z.names
A string vector for the variable names in z.
yx.names
A string vector for the variable names in yx.
olink
A character string naming the link function in the outcome nuisance
model.
elink
A character string naming the link function in the outcome nuisance
model.
cond
A logical value indicating whether cluster-specific intercepts should
be assumed. If TRUE, the is no column for the intercept in
v and z. Outcome concordant will also be removed.
oterms
The terms object corresponding to the outcome
nuisance model.
eterms
The terms object corresponding to the exposure
nuisance model.