print.survfit(x, scale=1)
survfit
function.
scale=365
would scale the printout to years.
x
,
with the invisible flag set to prevent printing.
The mean and its variance are based on a truncated estimator. That is, if the
last observation(s) is not a death, then the survival curve estimate does not
go to zero and the mean is undefined. In such a case, the estimator is based
on an assumption that the true curve goes to zero just beyond the last
observed follow up time; it will systematically underestimate the true mean.
The median and its confidence interval are defined by drawing a horizontal
line at 0.5 on the plot of the survival curve and its confidence bands.
The intersection of the line with the lower CI band defines the lower limit
for the median's interval, and similarly for the upper band. If any of the
intersections is not a point, then we use the smallest point of intersection,
e.g., if the survival curve were exactly equal to 0.5 over an interval.
Miller, Rupert G., Jr. (1981). Survival Analysis. New York:Wiley, p 71.