\HeaderA{survfit.object}{Survival Curve Object}{survfit.object}
\keyword{survival}{survfit.object}
\begin{Description}\relax
This class of objects is returned by the \code{survfit} class of functions
to represent a fitted survival curve. 

Objects of this class have methods for the functions \code{print},
\code{summary}, \code{plot}, \code{points} and \code{lines}. The
\code{\LinkA{print.survfit}{print.survfit}} method does more computation than is typical
for a print method and is documented on a separate page.
\end{Description}
\begin{Section}{COMPONENTS}
The following components must be included in a legitimate \code{survfit} object.
\describe{
\item[time] the time points at which the curve has a step.

\item[n.risk] the number of subjects at risk at t.

\item[n.event] the number of events that occur at time t.

\item[surv] the estimate of survival at time t+0.
This may be a vector or a matrix.

\item[strata] if there are multiple curves, this component gives the number of elements of
the \code{time} etc. vectors corresponding to the first curve, the second curve,
and so on.  The names of the elements are labels for the curves.

\item[std.err] the standard error of the cumulative hazard or -log(survival).

\item[upper] upper confidence limit for the survival curve.

\item[lower] lower confidence limit for the survival curve.

\item[conf.type] the approximation used to compute the confidence limits.

\item[conf.int] the level of the confidence limits, e.g. 90 or 95\%.

\item[na.action] the returned value from the na.action function, if any.  It will be used
in the printout of the curve, e.g., the number of observations deleted due
to missing values.

\item[call] the call that produced the object.
}
\end{Section}
\begin{Section}{SUBSCRIPTS}
Survfit objects that contain multiple survival curves can be subscripted.
This is most often used to plot a subset of the curves.
Usually a single subscript will be used.  In one particular case --
survival curves for multiple covariate values, from a Cox model that includes
a \code{strata} statement -- there is a matrix of curves and 2 subscripts may
be used.
(In this case \code{summary.survfit} will also print the data as a matrix).
\end{Section}
\begin{SeeAlso}\relax
\code{\LinkA{survfit}{survfit}}, \code{\LinkA{plot.survfit}{plot.survfit}},
\code{\LinkA{summary.survfit}{summary.survfit}}, \code{\LinkA{print.survfit}{print.survfit}}.
\end{SeeAlso}