survival: cluster – R documentation

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cluster

Identify clusters.

Description

This is a special function used in the context of survival models. It identifies correlated groups of observations, and is used on the right hand side of a formula. This style is now discouraged, use the cluster option instead.

Usage

cluster(x)

Arguments

`x`	A character, factor, or numeric variable.

Details

The function's only action is semantic, to mark a variable as the cluster indicator. The resulting variance is what is known as the “working independence” variance in a GEE model. Note that one cannot use both a frailty term and a cluster term in the same model, the first is a mixed-effects approach to correlation and the second a GEE approach, and these don't mix.

Value

x

Examples

marginal.model <- coxph(Surv(time, status) ~ rx, data= rats, cluster=litter,
                         subset=(sex=='f'))
frailty.model  <- coxph(Surv(time, status) ~ rx + frailty(litter), rats,
                         subset=(sex=='f'))

survival

Survival Analysis

v3.2-11

LGPL (>= 2)

Authors

Terry M Therneau [aut, cre], Thomas Lumley [ctb, trl] (original S->R port and R maintainer until 2009), Atkinson Elizabeth [ctb], Crowson Cynthia [ctb]

Initial release

2021-04-25