Peter Langfelder
2022-Jul-02 06:18 UTC
[R] Subsetting a vector using an index with all missing values
Ah, thanks, that makes sense. Peter On Fri, Jul 1, 2022 at 10:01 PM Bill Dunlap <williamwdunlap at 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 at 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code.
Ebert,Timothy Aaron
2022-Jul-02 14:47 UTC
[R] Subsetting a vector using an index with all missing values
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 at r-project.org> On Behalf Of Peter
Langfelder
Sent: Saturday, July 2, 2022 2:19 AM
To: Bill Dunlap <williamwdunlap at gmail.com>
Cc: r-help <r-help at 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 at 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 at
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 at 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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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&eand
provide commented, minimal, self-contained, reproducible code.