Windows XP R 2.8.1 I am trying to use anova(fitCont,fitCat) to compare two Cox models (coxph) one in which age is entered as a continuous variable, and a second where age is entered as a three-level factor (young, middle, old). The Analysis of Deviance Table produced by anova does not give a p value. Is there any way to get anova to produce p values?
Thank you, John Sorkin ANOVA results are pasted below: > anova(fitCont,fitCat) Analysis of Deviance Table Model 1: Surv(Time30, Died) ~ Rx + Age Model 2: Surv(Time30, Died) ~ Rx + AgeGrp Resid. Df Resid. Dev Df Deviance 1 62 147.38 2 61 142.38 1 5.00 The entire program including the original coxph models follows: > fitCont<-coxph(Surv(Time30,Died)~Rx+Age,data=GVHDdata) > summary(fitCont) Call: coxph(formula = Surv(Time30, Died) ~ Rx + Age, data = GVHDdata) n= 64 coef exp(coef) se(coef) z p Rx 1.375 3.96 0.5318 2.59 0.0097 Age 0.055 1.06 0.0252 2.19 0.0290 exp(coef) exp(-coef) lower .95 upper .95 Rx 3.96 0.253 1.40 11.22 Age 1.06 0.946 1.01 1.11 Rsquare= 0.154 (max possible= 0.915 ) Likelihood ratio test= 10.7 on 2 df, p=0.00483 Wald test = 9.46 on 2 df, p=0.0088 Score (logrank) test = 10.2 on 2 df, p=0.00626 > fitCat<-coxph(Surv(Time30,Died)~Rx+AgeGrp,data=GVHDdata) > summary(fitCat) Call: coxph(formula = Surv(Time30, Died) ~ Rx + AgeGrp, data = GVHDdata) n= 64 coef exp(coef) se(coef) z p Rx 1.19 3.27 0.525 2.26 0.024 AgeGrp[T.(15,25]] 1.98 7.26 0.771 2.57 0.010 AgeGrp[T.(25,45]] 1.61 5.02 0.806 2.00 0.045 exp(coef) exp(-coef) lower .95 upper .95 Rx 3.27 0.306 1.17 9.16 AgeGrp[T.(15,25]] 7.26 0.138 1.60 32.88 AgeGrp[T.(25,45]] 5.02 0.199 1.04 24.38 Rsquare= 0.217 (max possible= 0.915 ) Likelihood ratio test= 15.7 on 3 df, p=0.00133 Wald test = 12.0 on 3 df, p=0.0075 Score (logrank) test = 14.5 on 3 df, p=0.00232 > anova(fitCont,fitCat) Analysis of Deviance Table Model 1: Surv(Time30, Died) ~ Rx + Age Model 2: Surv(Time30, Died) ~ Rx + AgeGrp Resid. Df Resid. Dev Df Deviance 1 62 147.38 2 61 142.38 1 5.00 John David Sorkin M.D., Ph.D. Chief, Biostatistics and Informatics University of Maryland School of Medicine Division of Gerontology Baltimore VA Medical Center 10 North Greene Street GRECC (BT/18/GR) Baltimore, MD 21201-1524 (Phone) 410-605-7119 (Fax) 410-605-7913 (Please call phone number above prior to faxing) Confidentiality Statement: This email message, including any attachments, is for th...{{dropped:6}} ______________________________________________ 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.