This function is invoked and controlled by plot.prodlim.
markTime(x, times, nlost, pch, col, ...)Nil
The values of the curves at times.
The times where there curves are plotted.
The number of subjects lost to follow-up (censored) at
times.
The symbol used to mark the curves.
The color of the symbols.
Arguments passed to points.
Thomas Alexander Gerds <tag@biostat.ku.dk>
This function should not be called directly. The arguments can be specified
as atRisk.arg in the call to plot.prodlim.
plot.prodlim, confInt,
atRisk