In reply to suggestion by David W., setting an offset parameter doesn't seem to work as R is not recognizing the "X2" part of coxph( Surv(Time,Censor)~X1, offset=log(4.3*X2), data= a ). Also, here's some sample data:
X1 X2 Time Censor 1 1 0.40619454 77.00666 0 2 1 0.20717868 100.00000 0 3 1 0.77360963 79.03463 1 4 1 0.62221954 100.00000 0 5 1 0.32191280 100.00000 0 6 1 0.73790704 72.84842 0 7 1 0.65012237 100.00000 0 8 1 0.71596105 100.00000 0 9 1 0.74787202 84.00172 0 10 1 0.66803790 41.65760 0 11 1 0.79922364 92.41999 0 12 1 0.76433736 90.99983 0 13 1 0.57014524 100.00000 0 14 1 0.39642235 100.00000 0 15 1 0.55756045 100.00000 0 16 0 0.60079340 100.00000 0 17 0 0.43630695 100.00000 0 18 0 0.09388013 100.00000 0 19 0 0.55956791 100.00000 0 20 0 0.52491597 97.71884 1 where we set the coefficient of X2 to be 8. RWilliam wrote: > > Sorry for being impatient but is there really no way of doing this at all? > It's quite urgent so any help is very much appreciated. Thank you. > > > > RWilliam wrote: >> >> Hello, >> >> I just started using R to do epidemiologic simulation research using the >> Cox proportional hazard model. I have 2 covariates X1 and X2 which I want >> to model as h(t,X)=h0(t)*exp(b1*X1+b2*X2). I assume independence of X >> from t. >> >> After I simulate Time and Censor data vectors denoting the censoring time >> and status respectively, I can call the following function to fit the >> data into the Cox model (a is a data.frame containing 4 columns X1, X2, >> Time and Censor): >> b = coxph (Surv (Time, Censor) ~ X1 + X2, data = a, method = "breslow"); >> >> Now the purpose of me doing simulation is that I have another mechanism >> to generate the number b2. From the given b2 (say it's 4.3), Cox model >> can be fit to generate b1 and check how feasible the new model is. Thus, >> my question is, how do I specify such a model that is partially completed >> (as in b2 is known). I tried things like Surv(Time,Censor)~X1+4.3*X2, but >> it's not working. Thanks very much. >> > > -- View this message in context: http://old.nabble.com/How-do-I-specify-a-partially-completed-survival-analysis-model--tp26421391p26443562.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.