R devel - Nov 2008 - names generated in list indexing

Dear R-devel,

When a character vector is used to subscript a list and when some of the
subscripts are not present in the list names R  returns NULL for those
subscripts and generate NA names for each of them:
> list(b=1)[c('a','b')]
$<NA>  <<-- generated name
NULL
$b
[1] 1


Wouldn't it be more intuitive to use the subscript name rather than to
generate an NA? Something like this (not real result):
> list(b=1)[c('a','b')]
$a        <<-- more intuitive name
NULL
$b
[1] 1

> version
               _
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          7.1
year           2008
month          06
day            23
svn rev        45970
language       R
version.string R version 2.7.1 (2008-06-23)
>

Thanks,
Vadim

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Also note the behavior is the same for a non-list vector:
> c(b=1)[c('a','b')]
<NA>    b
  NA    1

but differs for a data frame:
> data.frame(b=1)[c('a','b')]
Error in `[.data.frame`(data.frame(b = 1), c("a", "b")) :
  undefined columns selected


On Fri, Nov 28, 2008 at 2:03 PM, Vadim Ogranovich
<vogranovich at jumptrading.com> wrote:
> Dear R-devel,
>
> When a character vector is used to subscript a list and when some of the
subscripts are not present in the list names R  returns NULL for those
subscripts and generate NA names for each of them:
>
>> list(b=1)[c('a','b')]
> $<NA>  <<-- generated name
> NULL
> $b
> [1] 1
>
>
> Wouldn't it be more intuitive to use the subscript name rather than to
generate an NA? Something like this (not real result):
>> list(b=1)[c('a','b')]
> $a        <<-- more intuitive name
> NULL
> $b
> [1] 1
>
>
>> version
>               _
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          7.1
> year           2008
> month          06
> day            23
> svn rev        45970
> language       R
> version.string R version 2.7.1 (2008-06-23)
>>
>
>
> Thanks,
> Vadim
>
> ________________________________
> Note: This email is for the confidential use of the named addressee(s) only
and may contain proprietary, confidential or privileged information. If you are
not the intended recipient, you are hereby notified that any review,
dissemination or copying of this email is strictly prohibited, and to please
notify the sender immediately and destroy this email and any attachments. Email
transmission cannot be guaranteed to be secure or error-free. Jump Trading,
therefore, does not make any guarantees as to the completeness or accuracy of
this email or any attachments. This email is for informational purposes only and
does not constitute a recommendation, offer, request or solicitation of any kind
to buy, sell, subscribe, redeem or perform any type of transaction of a
financial product.
>
>        [[alternative HTML version deleted]]
>
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