[R] Subsetting a vector using an index with all missing values
peter@|@ng|e|der @end|ng |rom gm@||@com
Sat Jul 2 08:18:56 CEST 2022
Ah, thanks, that makes sense.
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) ]
>  NA NA NA
> > x[ rep(NA, 3) ]
>  NA NA NA NA NA NA NA NA NA NA
> 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)]
>>  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]
>>  NA NA NA
>> but I'm wondering if the behaviour above is intended.
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