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 2.20
Index]