From ripley@stats.ox.ac.uk  Wed Sep 19 15:47:40 2001
From: ripley@stats.ox.ac.uk (ripley@stats.ox.ac.uk)
Date: Wed, 19 Sep 2001 16:47:40 +0200 (MET DST)
Subject: [Rd] missing() (PR#1096)
Message-ID: <200109191447.QAA28531@pubhealth.ku.dk>

>From the FAQ:

   * In S, `missing(ARG)' remains `TRUE' if ARG is subsequently modified;
     in R it doesn't.


>From ?missing in 1.3.1:

Details:

     `missing(x)' is only reliable if `x' has not been altered since
     entering the function: in particular it will always be true after
     `x <- match.arg(x)'.

My guess is that whatever you were looking at has been changed in the
current version.


On Wed, 19 Sep 2001 hosking@watson.ibm.com wrote:

> Full_Name: J. R. M. Hosking
> Version: 1.3.0
> OS: Windows 2000
> Submission from: (NULL) (198.81.209.16)
>
>
> R documentation suggests that if a function argument x is omitted,
> missing(x) should return TRUE even if x is subsequently assigned a value.
> This happens in S-plus.  But in R:
>
> > test
> function(x){
> print(missing(x))
> if(missing(x)) x<-0
> print(missing(x))
> invisible()
> }
> > test()
> [1] TRUE
> [1] FALSE
> >
>
>
> -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
> r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-devel-request@stat.math.ethz.ch
> _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
>

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-devel-request@stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._


[Rd] missing() (PR#1096)
ripley@stats.ox.ac.uk