[Rd] as.character(list(NA))

[William Dunlap]

I tend to avoid using as.<type> functions on lists, since they act oddly in
several ways.
E.g, if the list "L" consists entirely of scalar elements then
as.numeric(L) acts like
as.numeric(unlist(L)) but if any element is not a scalar there is an
error.  as.character()
does not seem to make a distinction between the all-scalar and
not-all-scalar cases
but does various things with NA's of various types.

Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Mon, Jan 22, 2018 at 11:14 AM, Robert McGehee <
rmcgehee at walleyetrading.net> wrote:

> Also perhaps a surprise that the behavior depends on the mode of the NA.
>
> > is.na(as.character(list(NA_real_)))
> [1] FALSE
> > is.na(as.character(list(NA_character_)))
> [1] TRUE
>
> Does this mean deparse() preserves NA-ness for NA_character_ but not
> NA_real_?
>
>
> -----Original Message-----
> From: R-devel [mailto:r-devel-bounces at r-project.org] On Behalf Of Hervé
> Pagès
> Sent: Monday, January 22, 2018 2:01 PM
> To: William Dunlap <wdunlap at tibco.com>; Patrick Perry <
> pperry at stern.nyu.edu>
> Cc: r-devel at r-project.org
> Subject: Re: [Rd] as.character(list(NA))
>
> On 01/20/2018 08:24 AM, William Dunlap via R-devel wrote:
> > I believe that for a list as.character() applies deparse()  to each
> element
> > of the list.  deparse() does not preserve NA-ness, as it is intended to
> > make text that the parser can read.
> >
> >> str(as.character(list(Na=NA, LglVec=c(TRUE,NA),
> > Function=function(x){x+1})))
> >   chr [1:3] "NA" "c(TRUE, NA)" "function (x) \n{\n    x + 1\n}"
> >
>
> This really comes as a surprise though since coercion to all the
> other atomic types (except raw) preserve the NAs.
>
> And also as.character(unlist(list(NA))) preserves them.
>
> H.
>
> >
> > Bill Dunlap
> > TIBCO Software
> > wdunlap tibco.com
> >
> > On Sat, Jan 20, 2018 at 7:43 AM, Patrick Perry <pperry at stern.nyu.edu>
> wrote:
> >
> >> As of R Under development (unstable) (2018-01-19 r74138):
> >>
> >>> as.character(list(NA))
> >> [1] "NA"
> >>
> >>> is.na(as.character(list(NA)))
> >> [1] FALSE
> >>
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> --
> Hervé Pagès
>
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
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>
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