untangle.specials: Help Process the 'specials' Argument of the 'terms' Function.

Description Usage Arguments Value Examples

View source: R/untangle.specials.R

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

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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

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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 documentation built on Aug. 24, 2021, 5:06 p.m.