st: How to proceed a landmark survival analysis (tests and plots)?

[Änne Glass <aenne.glass@uni-rostock.de>]

Hello Statalist,

we are interested in doing a landmark survival analysis with 
Stata(10.1), comparing therapy1 vs therapy2, before and after a landmark 
(t=24 months). Our data table consists of id, survivalTime, 
survivalStatus, therapyGroup.

Following your blog at 
http://www.stata.com/statalist/archive/2011-02/msg00207.html we did
1)  -stset- for declaring data to be survival-time data with _st, _d, 
__t, _t0. (done)
2)  -stsplit- to split data into 2 time-span records with the landmark 
t=24, that means one pre-landmark and one post-landmark. This step 
modified our data table by adding one line for those ids going over 24 
months. (done)
3)  -sts graph- command plotted the Kaplan-Meier failure function for 
the whole time-span (0-102 months) for both treatments. (done, but not 
desired)

A step-by-step approach would be great, as we are not yet that 
proficient in Stata.
Many thanks in advance - Aenne.
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/