Sort survival objects into a partial order, which is the same one
used internally for many of the calculations.

Usage

# S3 method for Surv
xtfrm(x)

Value

a vector of integers which will have the same sort order as

x.

Arguments

x

a Surv object

Author

Terry Therneau

Details

This creates a partial ordering of survival objects.
The result is sorted in time order, for tied pairs of times right censored
events come after observed events (censor after death), and left
censored events are sorted before observed events.
For counting process data (tstart, tstop, status) the ordering
is by stop time, status, and start time, again with censoring last.
Interval censored data is sorted using the midpoint of each interval.

The xtfrm routine is used internally by order and
sort, so these results carry over to those routines.