frailty.t(x, sparse=T, theta, df, eps=1e-05, tdf=5,
method=c("aic", "df", "fixed"), ...)
"fixed" method requires that
theta be given explicitly (and is assumed
when
"theta" is specified), the
"df" method is used when degrees of freedom
is explicitly set.
The
"aic" method chooses the variance (and hence the degrees of freedom)
based on Akaike's information criteria.
trace=T is the most
usual.
(The set of available arguments depends on the specific control function).
For the AIC method the
"caic=T" argument may be used to choose the corrected
AIC criteria.
"coxph.penal".
When using frailty terms with a
survReg model,
only
method="aic" should be used.
The
method argument can be set
in the call to
frailty in the formula.
The
method argument will be passed down to the specific
frailty function via the
... argument.
fit1 <- coxph(Surv(time, status) ~ age + sex + frailty(inst, df=4,
dist='t'), data=lung, na.action=na.exclude)
round(fit1$frail,3)