Strip special functions from terms
Reformulate a terms object such that some specials are stripped off
strip.terms(terms, specials, alias.names = NULL, unspecials = NULL, arguments, keep.response = TRUE)
terms |
Terms object |
specials |
Character vector of specials which should be stripped off |
alias.names |
Optional. A named list with alias names for the specials. |
unspecials |
Optional. A special name for treating all the unspecial terms. |
arguments |
A named list of arguments, one for each element
of specials. Elements are passed to |
keep.response |
Keep the response in the resulting object? |
This function is used to remove special specials, i.e., those which cannot or should not be evaluated. IMPORTANT: the unstripped terms need to know about all specials including the aliases. See examples.
Reformulated terms object with an additional attribute which contains the stripped.specials.
Thomas A. Gerds <tag@biostat.ku.dk>
parseSpecialNames reformulate drop.terms
## parse a survival formula and identify terms which
## should be treated as proportional or timevarying:
f <- Surv(time,status)~age+prop(factor(edema))+timevar(sex,test=0)+prop(bili,power=1)
tt <- terms(f,specials=c("prop","timevar"))
attr(tt,"specials")
st <- strip.terms(tt,specials=c("prop","timevar"),arguments=NULL)
formula(st)
attr(st,"specials")
attr(st,"stripped.specials")
## provide a default value for argument power of proportional treatment
## and argument test of timevarying treatment:
st2 <- strip.terms(tt,
specials=c("prop","timevar"),
arguments=list("prop"=list("power"=0),"timevar"=list("test"=0)))
formula(st2)
attr(st2,"stripped.specials")
attr(st2,"stripped.arguments")
## treat all unspecial terms as proportional
st3 <- strip.terms(tt,
unspecials="prop",
specials=c("prop","timevar"),
arguments=list("prop"=list("power"=0),"timevar"=list("test"=0)))
formula(st3)
attr(st3,"stripped.specials")
attr(st3,"stripped.arguments")
## allow alias names: strata for timevar and tp, const for prop.
## IMPORTANT: the unstripped terms need to know about
## all specials including the aliases
f <- Surv(time,status)~age+const(factor(edema))+strata(sex,test=0)+prop(bili,power=1)+tp(albumin)
tt2 <- terms(f,specials=c("prop","timevar","strata","tp","const"))
st4 <- strip.terms(tt2,
specials=c("prop","timevar"),
unspecials="prop",
alias.names=list("timevar"="strata","prop"=c("const","tp")),
arguments=list("prop"=list("power"=0),"timevar"=list("test"=0)))
formula(st4)
attr(st4,"stripped.specials")
attr(st4,"stripped.arguments")
## test if alias works also without unspecial argument
st5 <- strip.terms(tt2,
specials=c("prop","timevar"),
alias.names=list("timevar"="strata","prop"=c("const","tp")),
arguments=list("prop"=list("power"=0),"timevar"=list("test"=0)))
formula(st5)
attr(st5,"stripped.specials")
attr(st5,"stripped.arguments")
library(survival)
data(pbc)
model.design(st4,data=pbc[1:3,],specialsDesign=TRUE)
model.design(st5,data=pbc[1:3,],specialsDesign=TRUE)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.