Identify Clusters

DESCRIPTION:

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) 

REQUIRED ARGUMENTS:

x
A character, factor, or numeric variable.

VALUE:

x

DETAILS:

The function's only action is semantic, to mark a variable as the cluster indicator.

SEE ALSO:

, .

EXAMPLES:

coxph(Surv(futime, fustat) ~ age + cluster(rx), data = ovarian)