Returns the variance-covariance matrix of the parameter estimates of a fitted gcrq model object.
# S3 method for gcrq
vcov(object, term, type=c("sandw","boot"), ...)
A list (its length equal the length of tau
specified in gcrq
) of square matrices. Namely the list includes the covariance matrices of the parameter estimates for each regression quantile curve.
a fitted model object of class "gcrq"
returned by gcrq()
.
if specified, the returned covariance matrix includes entries relevant to parameter estimates for that 'term' only. If missing, the returned matrices refer to all model parameter estimates. Currently term
is not allowed.
Which cov matrix should be returned? 'boot'
means case-resampling bootstrap (see n.boot
in gcrq()
), 'sandw'
mean via the
sandwich formula.
additional arguments.
Vito Muggeo
Bootstrap-based covariance matrix, i.e. type="boot"
, is computable only if the object fit has been obtained by specifying n.boot>0
in gcrq()
.
summary.gcrq