cox.tvc.Rd
\name{cox.tvc}
\alias{cox.tvc}
\title{Test for a time-varying effect in the \code{coxph} model}
\description{
Test for a time-varying effect in the \code{coxph} model by re-fitting
the partial likelihood including a time-varying effect, plot
the effect size, and return the re-fitted model. The
main advantage of this function over the \code{tt()} special is
that it scales well for moderate sized datasets
(cf. \code{tt} which expands the dataset and scales very poorly).
}
\usage{
cox.tvc(obj, var=NULL, method="logt")
}
\arguments{
\item{obj}{A \code{coxph} object. Currently restricted to right
censoring with Breslow ties and without stratification, etc.}
\item{var}{String for the effect name. Currently assumes simple
continuous effects.}
\item{method}{A string representing the possible time
transformations. Currently only "logt".}
}
\value{
Returns a \code{tvcCoxph} object (which inherits from the \code{mle2} class) of the re-fitted model.
}
\seealso{
\code{\link{coxph}}, \code{\link{cox.zph}}
}
%% \references{
%% }
\examples{
## As per the example for cox.zph:
fit <- coxph(Surv(futime, fustat) ~ age + ecog.ps,
data=ovarian)
temp <- rstpm2:::cox.tvc(fit, "age")
print(temp) # display the results
plot(temp) # plot curves
}
\keyword{time-varying,Cox}