[R] Subsetting a vector using an index with all missing values
Bill Dunlap
w||||@mwdun|@p @end|ng |rom gm@||@com
Sat Jul 2 17:24:46 CEST 2022
Perhaps it should be an error if the length of a logical subscript is
bigger than the dimension it is subscripting. Currently in that case, x is
extended (with NA or NULL) to the length of the logical subscript. I doubt
this is desired very often.
> dput((1:3)[c(FALSE,FALSE,FALSE,TRUE,TRUE)])
c(NA_integer_, NA_integer_)
> dput((1:3)[c(FALSE,FALSE,TRUE,FALSE,TRUE)])
c(3L, NA)
-Bill
On Sat, Jul 2, 2022 at 7:49 AM Ebert,Timothy Aaron <tebert using ufl.edu> wrote:
> That nicely explains the difference in outcome between
> x[rep(TRUE,3)]
> x[rep("TRUE",3)]
>
>
> I do not quite get it.
> x<-1:10
> x[rep(x<2,3)]
> [1] 1 NA NA
> The length is three
>
> but
> x[rep(x>2,3)]
> [1] 3 4 5 6 7 8 9 10 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
> NA
> The length is 24
>
> Tim
> -----Original Message-----
> From: R-help <r-help-bounces using r-project.org> On Behalf Of Peter Langfelder
> Sent: Saturday, July 2, 2022 2:19 AM
> To: Bill Dunlap <williamwdunlap using gmail.com>
> Cc: r-help <r-help using r-project.org>
> Subject: Re: [R] Subsetting a vector using an index with all missing values
>
> [External Email]
>
> Ah, thanks, that makes sense.
>
> Peter
>
> On Fri, Jul 1, 2022 at 10:01 PM Bill Dunlap <williamwdunlap using gmail.com>
> wrote:
> >
> > This has to do with the mode of the subscript - logical subscripts are
> > repeated to the length of x and integer/numeric ones are not. NA is
> > logical, NA_integer_ is integer, so we get
> >
> > > x <- 1:10
> > > x[ rep(NA_integer_, 3) ]
> > [1] NA NA NA
> > > x[ rep(NA, 3) ]
> > [1] NA NA NA NA NA NA NA NA NA NA
> >
> > -Bill
> >
> >
> > On Fri, Jul 1, 2022 at 8:31 PM Peter Langfelder <
> peter.langfelder using gmail.com> wrote:
> >>
> >> Hi all,
> >>
> >> I stumbled on subsetting behavior that seems counterintuitive and
> >> perhaps is a bug. Here's a simple example:
> >>
> >> > x = 1:10
> >> > x[ rep(NA, 3)]
> >> [1] NA NA NA NA NA NA NA NA NA NA
> >>
> >> I would have expected 3 NAs (the length of the index), not 10 (all
> >> values in x). Looked at the documentation for the subsetting operator
> >> `[` but found nothing indicating that if the index contains all
> >> missing data, the result is the entire vector.
> >>
> >> I can work around the issue for a general 'index' using a somewhat
> >> clunky but straightforward construct along the lines of
> >>
> >> > index = rep(NA, 3)
> >> > x[c(1, index)][-1]
> >> [1] NA NA NA
> >>
> >> but I'm wondering if the behaviour above is intended.
> >>
> >> Thanks,
> >>
> >> Peter
> >>
> >> ______________________________________________
> >> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mai
> >> lman_listinfo_r-2Dhelp&d=DwICAg&c=sJ6xIWYx-zLMB3EPkvcnVg&r=9PEhQh2kVe
> >> AsRzsn7AkP-g&m=5kixibKMuZiVbTFd2D5fSZBYO3aFODtFyW96wUN-oC5gJtbOYJ9G0j
> >> 6zoo-P6z4W&s=WGGoTTZ6ENtmckv7K_B0OepH04TDjbiNp0D6IbdqpAg&e=
> >> PLEASE do read the posting guide
> >> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.o
> >> rg_posting-2Dguide.html&d=DwICAg&c=sJ6xIWYx-zLMB3EPkvcnVg&r=9PEhQh2kV
> >> eAsRzsn7AkP-g&m=5kixibKMuZiVbTFd2D5fSZBYO3aFODtFyW96wUN-oC5gJtbOYJ9G0
> >> j6zoo-P6z4W&s=JErkxZzuGa2y8pjLddJY5u_vDIbjw4tX1vzkb8LAe98&e=
> >> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Dhelp&d=DwICAg&c=sJ6xIWYx-zLMB3EPkvcnVg&r=9PEhQh2kVeAsRzsn7AkP-g&m=5kixibKMuZiVbTFd2D5fSZBYO3aFODtFyW96wUN-oC5gJtbOYJ9G0j6zoo-P6z4W&s=WGGoTTZ6ENtmckv7K_B0OepH04TDjbiNp0D6IbdqpAg&e=
> PLEASE do read the posting guide
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.org_posting-2Dguide.html&d=DwICAg&c=sJ6xIWYx-zLMB3EPkvcnVg&r=9PEhQh2kVeAsRzsn7AkP-g&m=5kixibKMuZiVbTFd2D5fSZBYO3aFODtFyW96wUN-oC5gJtbOYJ9G0j6zoo-P6z4W&s=JErkxZzuGa2y8pjLddJY5u_vDIbjw4tX1vzkb8LAe98&e=
> and provide commented, minimal, self-contained, reproducible code.
>
[[alternative HTML version deleted]]
More information about the R-help
mailing list