Skip to content

[Rcpp-devel] Initiate NumericMatrix in class constructor from S4 slot

3 messages · Romain Francois, Simon Zehnder

Original
Simon Zehnder
# 
Dear Rcpp-Devels,

I am a little confused right now with the following setting:

I have a C++ class with for example the following header

#include <RcppArmadillo.h>

class FirstClass {

	public:
		Rcpp::NumericMatrix M;
	
		FirstClass(Rcpp::S4& classS4);
		~FirstClass();
}

Then, in the .cc file I have:

#include <RcppArmadillo.h>
#include "FirstClass.h"

FirstClass::FirstClass(Rcpp::S4& classS4) {

	M(classS4.slot("M_R"));     // array M_R in R
 };

FirstClass::~FirstClass(){};

Now, my compiler always gives me an error: 

error: no match for call to ?(Rcpp::NumericMatrix {aka Rcpp::Matrix<14>}) (Rcpp::RObject::SlotProxy)?


Do I have to create the Matrix in the constructor differently? I want to reuse memory allocated in R. Further, could the error be triggered by M_R being an array in R? 

Best 

Simon
Romain Francois
# 
There is no constructor of Matrix tht takes a SlotProxy. You can do it in two steps perhaps. 

SEXP tmp = classS4.slot("M_R") ;
M = tmp ; 

Or use a specific cast:
In any case, you should use an initialisation list in your constructor anyway, something like:
Hiwever, i will add the missing constructor if this does not break anything else. 

Romain

Le 6 mars 2013 ? 08:14, Simon Zehnder <szehnder at uni-bonn.de> a ?crit :
Simon Zehnder
# 
Hi Romain,

first let me thank you for the very fast and informative answer!

I suppose, as SEXP is a pointer, that these attempts reuse the memory allocated in R, right? Further, I presume, that I proceed in the same way for lists from R to Rcpp, don't I?

In regard to the initialisation list:

I have in my class over 10 different objects, so up to now I refused to use the initialising list. But you are right, that in regard to performance (copying etc.) the
initialising list is indisputable. So I gonna use it. 

Thanks again Romain!

Best

Simon
On Mar 6, 2013, at 8:23 AM, Romain Francois <romain at r-enthusiasts.com> wrote: