[code]>require("survival")
> coxph(Surv(futime,fustat)~age + strata(rx),ovarian)
Call:
coxph(formula = Surv(futime, fustat) ~ age + strata(rx), data = ovarian)
coef exp(coef) se(coef) z p
age 0.137 1.15 0.0474 2.9 0.0038
Likelihood ratio test=12.7 on 1 df, p=0.000368 n= 26, number of events= 12
> coxph(Surv(futime,fustat)~age, ovarian, subset=rx==1)
Call:
coxph(formula = Surv(futime, fustat) ~ age, data = ovarian, subset = rx ==
1)
coef exp(coef) se(coef) z p
age 0.115 1.12 0.0456 2.52 0.012
Likelihood ratio test=8.68 on 1 df, p=0.00321 n= 13, number of events= 7
> coxph(Surv(futime,fustat)~age, ovarian, subset=rx==2)
Call:
coxph(formula = Surv(futime, fustat) ~ age, data = ovarian, subset = rx ==
2)
coef exp(coef) se(coef) z p
age 0.351 1.42 0.183 1.92 0.055
Likelihood ratio test=6 on 1 df, p=0.0143 n= 13, number of events= 5
[/code]
May I know why I cant separate
coxph(Surv(futime,fustat)~age + strata(rx),ovarian)
To be
coxph(formula = Surv(futime, fustat) ~ age, data = ovarian, subset = rx
== 1)
coxph(formula = Surv(futime, fustat) ~ age, data = ovarian, subset = rx
== 2)
May I know the difference of these issue? Many thanks...
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