[Rd] as.list method for by Objects
lawrence.michael at gene.com
Thu Feb 1 15:12:20 CET 2018
On Thu, Feb 1, 2018 at 1:21 AM, Martin Maechler <maechler at stat.math.ethz.ch>
> >>>>> Michael Lawrence <lawrence.michael at gene.com>
> >>>>> on Tue, 30 Jan 2018 10:37:38 -0800 writes:
> > I agree that it would make sense for the object to have c("by",
> "list") as
> > its class attribute, since the object is known to behave as a list.
> Well, but that (list behavior) applies to most non-simple S3
> classed objects, say "data.frame", say "lm" to start with real basic ones.
> The later part of the discussion, seems more relevant to me.
> Adding "list" to the class attribute seems as wrong to me as
> e.g. adding "double" to "Date" or "POSIXct" (and many more such cases).
There's a distinction though. Date and POSIXct should not really behave as
double values (an implementation detail), but "by" is expected to behave as
a list (when it is one).
For the present case, we should stay with focusing on is.list()
> being true after as.list() .. the same we would do with
> as.numeric() and is.numeric().
> > However, it would may be too disruptive to make this change at this
> > Hard to predict.
> > Michael
> > On Mon, Jan 29, 2018 at 5:00 PM, Dario Strbenac <
> dstr7320 at uni.sydney.edu.au>
> > 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
> >> and using class(result) == "list" is an alternative that only
> returns TRUE
> >> for lists. It's also confusing initially that
> >> > class(x)
> >>  "by"
> >> > is.list(x)
> >>  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
> >> Australia
> >> ______________________________________________
> >> R-devel at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
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