[Rcpp-devel] Array into C++ with cppFunction

[Dirk Eddelbuettel]

hi nick,

On 12 February 2014 at 09:23, Nick Menzies wrote:
| Hi Dirk, thanks for pointing me in the right direction. 
| 
| My solution below for a 3D array (documenting for rubes like myself).   N
| 
| library(Rcpp)
| library(RcppArmadillo)
| 
|     cppFunction('
|     double  NewFunc( NumericVector ArrayR ) {
|       IntegerVector DimsA = ArrayR.attr("dim");
|       arma::cube    ArrayC(ArrayR.begin(),DimsA[0],DimsA[1],DimsA
| [2],false);
|       double Output = ArrayC(1,2,3) + ArrayC(2,3,4);
|       return Output;      
|     }', depends="RcppArmadillo")
| 
|     NewFunc(array(1,dim=c(5,5,5))) # Test, works

Looks good -- do you want to roll this up with a paragraph or two of
motivation and explanation and submit to the Rcpp Gallery?

Dirk
 
 
 
| On Tue, Feb 11, 2014 at 3:34 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
| 
| 
|     (Resending, this time with CC to list. Sorry for the extra first post.
|     --Dirk)
| 
|     On 11 February 2014 at 11:49, Nick Menzies wrote:
|     | Is there a way to pass an array into c++ when using cppFunction?  I
|     realize
|     | arrays have been discussed a number of times, but the solutions I have
|     found
|     | (e.g. http://markovjumps.blogspot.com/2011/12/
|     | r-array-to-rcpparmadillo-cube.html, or https://www.mail-archive.com/
|     | rcpp-devel at lists.r-forge.r-project.org/msg05897.html) are described in
|     the
|     | context of cxxfunction, and I haven't been able to work how to implement
|     this
|     | with cppFunction.
| 
|     An array is just a vector with a dimension attribute. Treat it the same at
|     the C++ level.
| 
|     There are several posts at the Rcpp Gallery dealing with reading / setting
|     attributes, and you should know how to pass a single vector through.
| 
|     Dirk
| 
|     --
|     Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
| 
| 
| 
| 
| --
| 
| Nick Menzies
| nick.menzies at gmail.com
| 404 217 1076

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