[Rd] subset data.frame at C level

[Jim Hester]

It looks to me like internally .subset2 uses `get1index()`, but this
function is declared in Defn.h, which AFAIK is not part of the exported R
API.

 Looking at the code for `get1index()` it looks like it just loops over the
(translated) names, so I guess I just do that [0].

[0]:
https://github.com/r-devel/r-svn/blob/1ff1d4197495a6ee1e1d88348a03ff841fd27608/src/main/subscript.c#L226-L235

On Wed, Jun 17, 2020 at 6:11 AM Morgan Morgan <morgan.emailbox using gmail.com>
wrote:

> Hi,
>
> Hope you are well.
>
> I was wondering if there is a function at C level that is equivalent to
> mtcars$carb or .subset2(mtcars, "carb").
>
> If I have the index of the column then the answer would be VECTOR_ELT(df,
> asInteger(idx)) but I was wondering if there is a way to do it directly
> from the name of the column without having to loop over columns names to
> find the index?
>
> Thank you
> Best regards
> Morgan
>
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