[Rcpp-devel] Returning Armadillo matrices with dimnames

[Krzysztof Sakrejda]

On May 2, 2013 11:22 PM, "Dirk Eddelbuettel" <edd at debian.org> wrote:
>
>
> On 2 May 2013 at 17:24, Dirk Eddelbuettel wrote:
> | Sorry. It was just a quick guess.
> |
> | On second thought, I think your earlier approach was actually pretty
good:
> | Take your arma object, use wrap to turn it into a SEXP (or maybe an
RObject)
> | and you should then be able to set attributes.
>
> And on third thought, I think we both overlooked one aspect:
>
>  -- R and Rcpp can share objects, passing them back and forth efficiently
via
>     pointers as _both use the same allocation scheme_. So when Rcpp
creates
>     an object, it is "as if" R created it.  Which is why we can generally
>     move them back and forth.
>
>  -- That does not hold for Armadillo.  So to bring an Armadillo object
back,
>     we are better off making a copy.

Depending on the context, you could pre-create both matrices in R and pass
them in to Rcpp/Armadillo as Dirk suggests.   Manipulate them as necessary
and they are available back in R when you are done.

Krzysztof

>
> So once again the "No Free Lunch" theorem at work.  Sorry.
>
> Dirk
>
> --
> Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
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