survival: untangle.specials – R documentation

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

untangle.specials

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)

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