[Rd] as.list method for by Objects
gmbecker at ucdavis.edu
Tue Jan 30 23:33:24 CET 2018
What version of R are you using. In my mildly old 3.4.0 installation and in
the version of Revel I have lying around (also mildly old...) I don't see
the behavior I think you are describing
> b = by(1:2, 1:2, identity)
R Under development (unstable) (2017-12-19 r73926)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: OS X El Capitan 10.11.6
Matrix products: default
attached base packages:
 stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
As for by not having a class definition, no S3 class has an explicit
definition, so this is somewhat par for the course here...
did I misunderstand something?
On Tue, Jan 30, 2018 at 2:24 PM, Hervé Pagès <hpages at fredhutch.org> wrote:
> I agree that it makes sense to expect as.list() to perform
> a "strict coercion" i.e. to return an object of class "list",
> *even* on a list derivative. That's what as( , "list") does
> by default:
> # on a data.frame object
> as(data.frame(), "list") # object of class "list"
> # (but strangely it drops the names)
> # on a by object
> x <- by(warpbreaks[, 1:2], warpbreaks[,"tension"], summary)
> as(x, "list") # object of class "list"
> More generally speaking as() is expected to perform "strict
> coercion" by default, unless called with 'strict=FALSE'.
> That's also what as.list() does on a data.frame:
> as.list(data.frame()) # object of class "list"
> FWIW as.numeric() also performs "strict coercion" on an integer
> as.numeric(1:3) # object of class "numeric"
> So an as.list.env method that does the same as as(x, "list")
> would bring a small touch of consistency in an otherwise
> quite inconsistent world of coercion methods(*).
> (*) as(data.frame(), "list", strict=FALSE) doesn't do what you'd
> expect (just one of many examples)
> On 01/29/2018 05:00 PM, Dario Strbenac wrote:
>> Good day,
>> I'd like to suggest the addition of an as.list method for a by object
>> that actually returns a list of class "list". This would make it safer to
>> do type-checking, because is.list also returns TRUE for a data.frame
>> variable and using class(result) == "list" is an alternative that only
>> returns TRUE for lists. It's also confusing initially that
>>  "by"
>>  TRUE
>> since there's no explicit class definition for "by" and no mention if it
>> has any superclasses.
>> Dario Strbenac
>> University of Sydney
>> Camperdown NSW 2050
>> R-devel at r-project.org mailing list
> Hervé Pagès
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
> P.O. Box 19024
> Seattle, WA 98109-1024
> E-mail: hpages at fredhutch.org
> Phone: (206) 667-5791
> Fax: (206) 667-1319
> R-devel at r-project.org mailing list
Gabriel Becker, PhD
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