2025-01-12 04:36:52 +08:00

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R Under development (unstable) (2023-01-30 r83727) -- "Unsuffered Consequences"
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> # Tests for the drop.special function, which is not exported
> #
> library(survival)
> library(splines)
> dfun <- survival:::drop.special
>
> # In a terms structure, the factors attribute is a matrix with row and column
> # names. The predvars and dataClasses attributites, if present, index to the
> # row names; as do values of the specials attribute. The term.labels attribute
> # aligns with the column names.
>
> # For most model formula the row and column names nicely align, but not always.
> # [.terms, unfortunately, implicitly assumes that they do align. This means
> # that the result of subscripting is not always proper.
>
> # The coxph routine needs to drop terms such as strata, fraily, and cluster
> # from the terms structure BEFORE calling model.matrix, otherwise a huge
> # matrix could result, from which most of the columns would need to be
> # dropped. (A matched case-control fit will have n/2 strata).
>
> # The assumptions are correct for form1, fail for the others
> form0 <- terms(Surv(time, status) ~ age + ns(wt.loss) + strata(sex),
+ specials="strata")
> form1 <- terms(Surv(time, status) ~ age + ns(wt.loss) + strata(sex) -1,
+ specials="strata")
> form2 <- terms(Surv(time, status) ~ age + offset(ph.ecog) + ns(wt.loss) +
+ strata(sex), specials= "strata")
> form3 <- terms(Surv(time, status) ~ age + strata(sex)/ph.ecog + ns(wt.loss),
+ specials= "strata")
> form4 <- terms(~ age + meal.cal*ph.ecog - ph.ecog + strata(sex) + ns(wt.loss),
+ specials = "strata")
> form5 <- terms(~ age + ph.ecog - ph.ecog + strata(sex) + ns(wt.loss),
+ specials = "strata")
>
> test0 <- terms(model.frame(form0, data= lung))
> test1 <- terms(model.frame(form1, data= lung))
> test2 <- terms(model.frame(form2, data= lung))
> test3 <- terms(model.frame(form3, data= lung))
> test4 <- terms(model.frame(form4, data= lung))
> test5 <- terms(model.frame(form5, data= lung))
>
> ccheck <- function(term) {
+ aa <- attributes(term)
+ cname <- colnames(aa$factors)
+ rname <- rownames(aa$factors)
+ sindx <- aa$specials$strata
+ offset <- aa$offset
+ vname <- sapply(aa$variables, deparse)[-1]
+ pname <- sapply(aa$predvars, function(x) deparse(x, nlines=1))[-1]
+
+ # predvars contains an expanded form of ns(wt.loss), so only use the first
+ # 8 chars. The goal is to see if it is the right terms, in the right order
+ test <- c(vname= identical(rname, vname),
+ labels = identical(cname, aa$term.labels),
+ data = identical(rname, names(aa$dataClasses)),
+ predvars= identical(substr(pname, 1,8), substr(rname, 1,8)),
+ strata = any(grepl("strata", aa$term.labels)))
+
+ test
+ }
>
> # the untangle.specials was the first attempt to get subscripts right
> u0 <- untangle.specials(test0, 'strata')
> u1 <- untangle.specials(test1, 'strata')
> u2 <- untangle.specials(test2, 'strata')
> u3 <- untangle.specials(test3, 'strata')
> u4 <- untangle.specials(test4, 'strata')
> u5 <- untangle.specials(test5, 'strata')
>
> # The survival package, in various places, had used a [.terms to remove
> # the strata, via a newTerms <- Terms[-u0$terms] assignment where
> # Terms = terms(model-frame)
> # The newer drop.specials function, assigned as 'dfun' above, addresses
> # the issue.
> # All is well for test0 and test1: [.terms works as expected
> # In the remainder, some combination of a/b/c occurs with [.terms
> # a. the wrong variable gets dropped (serious),
> # b. the dataClasses attribute has too many elements (not serious).,
> # c. Predvars may be out of order (serious).
> #
> #
> ans1 <- c(TRUE, TRUE, TRUE, TRUE, FALSE) # correct answer for all but test3
> ans2 <- rep(TRUE, 5) # correct answer for test3
> names(ans1) <- names(ans2) <- c("vname", "labels", "data", "predvars", "strata")
>
> all.equal(ccheck(test0[-u0$terms]), ans1)
[1] TRUE
> all.equal(ccheck(test1[-u1$terms]), ans1)
[1] TRUE
> all.equal(ccheck(test2[-u2$terms]), ans1)
[1] "2 element mismatches"
> all.equal(ccheck(test3[-u3$terms]), ans2)
[1] "2 element mismatches"
> all.equal(ccheck(test4[-u4$terms]), ans1)
[1] "2 element mismatches"
> all.equal(ccheck(test5[-u5$terms]), ans1)
[1] "2 element mismatches"
>
> # The dropterms function works in all 6 cases
> all.equal(ccheck(dfun(test0, attr(test0, "specials")$strata)), ans1)
[1] TRUE
> all.equal(ccheck(dfun(test1, attr(test1, "specials")$strata)), ans1)
[1] TRUE
> all.equal(ccheck(dfun(test2, attr(test2, "specials")$strata)), ans1)
[1] TRUE
> all.equal(ccheck(dfun(test3, attr(test3, "specials")$strata)), ans2)
[1] TRUE
> all.equal(ccheck(dfun(test4, attr(test4, "specials")$strata)), ans1)
[1] TRUE
> all.equal(ccheck(dfun(test5, attr(test5, "specials")$strata)), ans1)
[1] TRUE
>
>
>
>
> proc.time()
user system elapsed
0.855 0.089 0.935