[Rcpp-devel] Returning an arma vec

[Gabor Grothendieck]

1. This returns a matrix rather than a vector:

--  start of file teste.cpp ---
#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]

using namespace arma;
using namespace Rcpp;

// [[Rcpp::export]]
NumericVector teste(const vec& x) {
vec v = x.subvec(1, 2); // x
return wrap(v); // x
}
/*** R
teste(1:4)
*/
--- end of file teste.cpp ---

Now run in R:

> sourceCpp("teste.cpp", rebuild = TRUE)

> teste(1:4)
     [,1]
[1,]    2
[2,]    3


2. If we replace the lines marked // x with

       return wrap(x.subvec(1, 2));

then it fails with a compiler error.

error: cannot convert 'const arma::subview_col<double>' to 'SEXP' in
initialization


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