untangle.specials {survival} R Documentation

## Help Process the ‘specials’ Argument of the ‘terms’ Function.

### Description

Given a terms structure and a desired special name, this returns an index appropriate for subscripting the terms structure and another appropriate for the data frame.

### Usage

untangle.specials(tt, special, order=1)


### Arguments

 tt a terms object. special the name of a special function, presumably used in the terms object. order the order of the desired terms. If set to 2, interactions with the special function will be included.

### Value

a list with two components:

 vars a vector of variable names, as would be found in the data frame, of the specials. terms a numeric vector, suitable for subscripting the terms structure, that indexes the terms in the expanded model formula which involve the special.

### Examples

formula <- Surv(tt,ss) ~ x + z*strata(id)
tms <- terms(formula, specials="strata")
## the specials attribute
attr(tms, "specials")
## main effects
untangle.specials(tms, "strata")
## and interactions
untangle.specials(tms, "strata", order=1:2)


[Package survival version 3.5-5 Index]