baseline survival in time-dependent model

["Perperoglou, A. (MStat)" <A.Perperoglou@lumc.nl>]

   Dear S-plus users,
after fitting a Cox time-dependent model I plot the survival function. I
know that S-plus estimates the Survival
at the mean value of the covariates, but what happens whith the time
dependent model?
What is the value of time that S-plus uses to estimate the survival
function?
Regards


Aris Perperoglou
Department of Medical Statistics
Leiden University Medical Center
P.O.Box 9604,  
2300 RC Leiden, The Netherlands
phone  +31-71-5276829
fax    +31-71-5276799
e-mail a.perperoglou@lumc.nl