Göran Broström wrote: > > > Good. Do you still need answers to your other questions? > >
Yes. Could answer the following two questions: 1- Can I use phreg function to estimate a model with time-dependent covariates? In case of a positive answer, how? 2- I could not find any example that clearly explains how to interpret aftreg output. Specially, refering to the diference between survreg and aftreg output (intercept and sign of the estimates). I include below an example of output of a regression with coxph, survreg, phreg and aftreg and a time-independent variable. I would appreciate if you could explain it or provide an external example that explains how it works. n=26 events=25 time at risk=45 a/ coxph(Surv(time,s) ~ Z1, data=data.frame(data)) coef exp(coef) se(coef) z p Z1 0.0249 1.03 0.00907 2.75 0.006 b/ phreg(Surv(time,s) ~ Z1, data=data.frame(data), dist="weibull") Covariate W.mean Coef Exp(Coef) se(Coef) Wald p Z1 43.689 0.033 1.033 0.009 0.000 log(scale) 0.641 1.899 0.065 0.000 log(shape) 1.172 3.230 0.158 0.000 Max. log. likelihood -22.135 LR test statistic 13.1 Degrees of freedom 1 Overall p-value 0.000302689 c/ aftreg(Surv(time,s) ~ Z1, data=data.frame(data), dist="weibull") Covariate W.mean Coef Exp(Coef) se(Coef) Wald p mas 43.689 0.010 1.010 0.002 0.000 log(scale) 1.147 3.149 0.141 0.000 log(shape) 1.172 3.230 0.158 0.000 Max. log. likelihood -22.135 LR test statistic 13.1 Degrees of freedom 1 Overall p-value 0.000302692 d/ survreg(Surv(time,s) ~ Z1, data=data.frame(data), dist="weibull") Value Std. Error z p (Intercept) 1.1476 0.13498 8.50 1.87e-17 mas -0.0101 0.00232 -4.34 1.45e-05 Log(scale) -1.1724 0.15787 -7.43 1.11e-13 Scale= 0.310 Weibull distribution Loglik(model)= -22.1 Loglik(intercept only)= -28.7 Chisq= 13.05 on 1 degrees of freedom, p= 3e-04 Number of Newton-Raphson Iterations: 5 Thank you very much, J -- View this message in context: http://r.789695.n4.nabble.com/AFT-model-time-dependent-with-weibull-distribution-tp3755079p3757387.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.