[Rcpp-devel] [RcppArmadillo] Result of Rcpp Wrap() for Sparse Matrix

[Serguei Sokol]

Le 14/06/2017 à 15:21, Douglas Bates a écrit :
> 
> 
> On Wed, Jun 14, 2017 at 3:59 AM Serguei Sokol <serguei.sokol at gmail.com <mailto:serguei.sokol at gmail.com>> wrote:
> 
>     Le 13/06/2017 à 18:24, Douglas Bates a écrit :
>      > On Tue, Jun 13, 2017 at 10:56 AM Binxiang Ni <binxiangni at gmail.com <mailto:binxiangni at gmail.com> <mailto:binxiangni at gmail.com
>     <mailto:binxiangni at gmail.com>>> wrote:
>      >
>      >     Hi,
>      >
>      >     I am working on fixing sparse matrix conversion for RcppArmadillo. Now a problem comes up to me: what kind of sparse matrix is expected to pass from
>      >     Armadillo to R? That is, what should the result of wrap() be? dgCMatrix(if logical, lgCMatrix or ngCMatrix)  or their original type?
>      >
>      >
>      > What do you mean by "their original type"?
>      >
>      > It seems that the correspondence is
>      > Armadillo           Matrix package
>      > sp_mat       <=> dgCMatrix
>      > sp_cx_mat <=> zgCMatrix
>      > sp_imat      <=> igCMatrix
>     I would also consider the format used in a package slam.
>     It simply stores the indexes and non-zero values in a triplet (i,j,v).
> 
> 
> That is the format of the dgTMatrix class from the Matrix package for R but not, as far as I can tell, in Armadillo.  A brief glance at the Armadillo 
> documentation indicates that sparse matrices are always in the compressed sparse column (CSC) format.
Indeed, but nothing prevents Binxiang to develop a wrap() that will convert
armadillo format to one or many of R formats, right?