[Rd] requireNamespace etiquette

RKoenker rkoenker at uiuc.edu
Fri Feb 20 22:15:57 CET 2015

I'm trying to resolve a problem of Namespaces and probably have misunderstood
something basic.
In my quantreg package the function crq() has as its first argument a
formula that typically contains
something like this: Surv(y, ...) ~ foo,  where Surv is a function from the
survival package which
quantreg suggests.  When this syntax is encountered in ordinary usage Surv
is resolved, I believe,
because near the beginning of the crq code there is the locution:

if(!requireNamespace("survival", quietly = TRUE))
        stop("crq requires survival package to be installed")

However, when R CMD check tries to do one of the crq examples I see:

> f <- crq(Surv(y,d,type = "left") ~ x, method = "Portnoy")
Error in eval(expr, envir, enclos) : could not find function "Surv"
Calls: crq ... eval -> model.frame -> model.frame.default -> eval -> eval
Execution halted

Can someone suggest a fix?


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