[Rd] data() misbehaving inside a function

Peter Dalgaard p.dalgaard at biostat.ku.dk
Thu Oct 16 21:08:27 MEST 2003

David James <dj at research.bell-labs.com> writes:

> Calls of the form data(package = pkg) inside a function 
> incorrectly fail ("pkg" is a local variable).  For instance,
>    foo <- function(pkg) data(package = pkg)
>    foo("base")
>    Error in .find.package(package, lib.loc, verbose = verbose) :
>            none of the packages were found

This is pretty much unavoidable if you want a function to accept
unquoted names. It's not in principle different from

women <- "airquality"

not being equivalent to data("airquality"). Some functions (library(),
require(), demo()) have a character.only argument to prevent it, and I
suppose we should consider putting it on help() and data() as well.
Meanwhile, my preferred device is

foo <- function(pkg) eval(substitute(data(package)))


   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

More information about the R-devel mailing list