[R] bug or feature?

ivo welch ivowel at gmail.com
Thu May 17 21:37:47 CEST 2007

of course it is.  virtually everything in R is somewhere documented,
and once one sees it, pretty well documented, too.

my suggestion for a warning is more a matter of "user
friendliness"---a warning, not an error.  chances are that if a
variable exists in the upper frames, and a user reuses it, there is a
good chance that it could be ambiguous.  for such cases, a user may be
well advised to use subset$variablename explicitly instead of simply
variablename IMHO.  I believe many C compilers and the perl
interpreter routinely issue warnings when there is a good chance that
a behavior may not necessarily be what a naive user might expect, even
though the code is perfectly correct and unambiguous.

of course, I am really NAIVE very often.



On 5/17/07, Bert Gunter <gunter.berton at gene.com> wrote:
> ... but it **is** explicitly documented in ?subset:
> "For data frames, the subset argument works on the rows. Note that subset
> will be evaluated in the data frame, so columns can be referred to (by name)
> as variables in the expression (see the examples). "
> Bert Gunter
> Genentech Nonclinical Statistics
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of ivo welch
> Sent: Thursday, May 17, 2007 11:53 AM
> To: jim holtman
> Cc: r-help
> Subject: Re: [R] bug or feature?
> ahh...it is the silent substitution of the data frame in the subset
> statement.   I should have known this.  (PS: this may not be desirable
> behavior; maybe it would be useful to issue a warning if the same name
> is defined in an upper data frame.  just an opinion...)
> mea misunderstanding.
> /iaw
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