An object of class **'surv_summary'**, which is a data frame with
the following columns:

time: the time points at which the
curve has a step.

n.risk: the number of subjects at risk at t.

n.event: the number of events that occur at time t.

n.censor: number
of censored events.

surv: estimate of survival.

std.err:
standard error of survival.

upper: upper end of confidence interval.

lower: lower end of confidence interval.

strata: stratification of survival curves.

In a situation, where survival curves have been fitted with one or more
variables, surv_summary object contains **extra columns** representing the
variables. This makes it possible to facet the output of
`ggsurvplot`

by strata or by some combinations of factors.

surv_summary object has also an attribut named **'table'** containing
information about the survival curves, including medians of survival with
confidence intervals, as well as, the total number of subjects and the
number of event in each curve.