Dear S users,
I have a question about the x vector in coxph. The input x variable has
value 1 and 0, representing treatment group and control group. I have 50
subjects in treatment group and 100 subjects in control group. Using a
model such as
coxout<-coxph(Surv(time,status)~x,mydata)
coxout$linear.pred returns a vector of 0.6021568 (each for 50 subjects
in the treatment group) and -0.3015784 (each for 100 subjects in the
control group), instead of a vector of 50 "beta estimator"s and 100 "0"s.
coxout$linear.pred is not equal to exp(beta*X). I wonder how splus handles
X variable. Since cumulative baseline hazard Ho is estimated as sum(# of
death/sum(exp(beta*X))) (1), the baseline hazard is also different
from the Ho calculated by plugging the final beta estimate, X and # of
death into (1).
Thanks for your help!
James
-----------------------------------------------------------------------
This message was distributed by s-news@wubios.wustl.edu. To unsubscribe
send e-mail to s-news-request@wubios.wustl.edu with the BODY of the
message: unsubscribe s-news
|