[Rcpp-devel] RcppEigen: Getting and setting dimnames of sparse matrix

[Dirk Eddelbuettel]

Hi Søren,

On 19 January 2013 at 08:45, Søren Højsgaard wrote:
| Dear Dirk
| 
| Thanks for your reply. Seems to me that there is an attr() method for for setting and retrieving attributes - but this is not available for sparse matrices. For sparse matrices there seems to be a slot() method that will retrieve but not set slots?

As I said in my message below, sparse matrices are S4 object so this may well
be different.  Did you try to set a slot value?

I also said that I don't work all that much with S4 in R (or Rcpp) but other
readers do so maybe someone has a trick.  I just glanced at S4.h which leads
you to SlotProxy in RObject.h, and looking at runit.S4.R also suggests it may
work.

Regards,  Dirk
 
| Regards
| Søren
| 
| -----Original Message-----
| From: Dirk Eddelbuettel [mailto:edd at debian.org] 
| Sent: 19. januar 2013 00:18
| To: Søren Højsgaard
| Cc: rcpp-devel at lists.r-forge.r-project.org
| Subject: Re: [Rcpp-devel] RcppEigen: Getting and setting dimnames of sparse matrix
| 
| 
| Hi Søren,
| 
| On 18 January 2013 at 23:07, Søren Højsgaard wrote:
| | Dear all,
| | I put a sparse "dgCMatrix" into RcppEigen code as a sparse matrix. In Rcpp I create a new matrix of same dimensions as the input matrix. I would like to copy the dimnames from the input matrix to the output matrix. Can this be done? (It is essential that I can stick to working with sparse matrices). I know that I can set the dimensions on the R-side, but that involves AFAIK copying the object which takes time. 
| 
| "It should".  
| 
| I have not worked all that much with sparse matrices, but dimnames etc are merely attributes at the R level.  And we read and write these just as easily at the C++ level. 
| 
| Have a look at few of the recent posts at   http://gallery.rcpp.org  
| in particular 
| 
|   http://gallery.rcpp.org/articles/getting-attributes-for-xts-example
| 
| and
| 
|   http://gallery.rcpp.org/articles/creating-xts-from-c%2B%2B
| 
| where I, respectively, "get" and "set" the attributes that make an xts
| object: dimnames, an index (itself with class and time zone attributes) and timezone and class info.
| 
| For sparse matrices the mechanics may be slighty different due to the S4-ness of things but the rest should work.  I put a feeble attempt at working with sparse matrices here:
| 
|   http://gallery.rcpp.org/articles/armadillo-sparse-matrix/
| 
| Maybe we can do something similar with richer 'matrix factory' functions for Eigen?
| 
| Dirk
| 
| | 
| | Example:
| | 
| | src<-'
| | using namespace Rcpp;
| | typedef Eigen::SparseMatrix<double> SpMat;
| | SpMat   X(as<SpMat>(XX_));
| | return(wrap(X));
| | '
| | 
| | names_ <- cxxfunction(signature(XX_="matrix"), plugin="RcppEigen",
| | 	body=src)
| | 
| | ugM	<- new("dgCMatrix"
| |     , i = c(1L, 0L, 2L, 1L)
| |     , p = c(0L, 1L, 3L, 4L)
| |     , Dim = c(3L, 3L)
| |     , Dimnames = list(c("a", "b", "c"), c("a", "b", "c"))
| |     , x = c(1, 1, 1, 1)
| |     , factors = list())
| | 
| | > ugM
| | 3 x 3 sparse Matrix of class "dgCMatrix"
| |   a b c
| | a . 1 .
| | b 1 . 1
| | c . 1 .
| | > 
| | > names_(ugM)
| | 3 x 3 sparse Matrix of class "dgCMatrix"
| |           
| | [1,] . 1 .
| | [2,] 1 . 1
| | [3,] . 1 .
| | 
| | Any advice? Thanks in advance
| | Søren
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| 
| --
| Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com  

-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com