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Message-ID: <1124389929.21569.5.camel@iron.libaux.ucsf.edu>
Date: 2005-08-18T18:32:09Z
From: Ross Boylan
Subject: problem with repeated formal arguments and  ...

I want to add an argument if it is not present.  Following the Green
Book, p. 337:
test <- function(x, ...){
  dots <- list(...)
  if (!hasArg(from))
    from <- 0
  else
    from <- dots$from
  curve(x, from=from, ...)
}

> test(sin)
> test(sin, from=4)
Error in curve(x, from = from, ...) : formal argument "from" matched by
multiple actual arguments

The FAQ says, in the section on differences between R and S,
"R disallows repeated formal arguments in function calls."

That seems a perfectly reasonable rule,  but how do I handle this
situation?

-- 
Ross Boylan                                      wk:  (415) 502-4031
530 Parnassus Avenue (Library) rm 115-4          ross at biostat.ucsf.edu
Dept of Epidemiology and Biostatistics           fax: (415) 476-9856
University of California, San Francisco
San Francisco, CA 94143-0840                     hm:  (415) 550-1062