TITLE(cluster @@ Identify clusters. )
This is a special function used in the context of the Cox model.  It
identifies correlated groups of observations, and is used on the right hand
side of a formula.
USAGE(
cluster(x)
)
ARGUMENTS(
ARG(x@@)
A character, factor, or numeric variable.
)
PARA BOLD(VALUE)
x
The function's only action is semantic, to mark a variable as the
cluster indicator.
PARA BOLD(SEE ALSO)
coxph
BLANK

PARA BOLD( )
BLANK

EXAMPLES(
coxph(Surv(futime, fustat) ~ age + cluster(group))
)
PARA ITALIC(File automatically converted from S(-PLUS) help format)
