[Rcpp-devel] Turning a vector into a matrix

[Søren Højsgaard]

Romain, 

I actually already tried this in my file util.cpp but can't get it to work:

#include <Rcpp.h>

using namespace Rcpp;

// [[Rcpp::export]]
NumericMatrix vec2matrix(NumericVector x, int nrow, int ncol) {
  return NumericMatrix(nrow, ncol, x.begin()); 
}

// [[Rcpp::export]]
template <int RTYPE>
Matrix<RTYPE> vec2matrix2(Vector<RTYPE> x, int nrow, int ncol) {
  return Matrix<RTYPE>(nrow, ncol, x.begin()); 
}

Any thoughts?
Søren



> Rcpp::sourceCpp('./util.cpp')
g++ -m64 -I"C:/programs/R/current/include" -DNDEBUG     -I"C:/programs/R/current/library/Rcpp/include"  -I"d:/RCompile/CRANpkg/extralibs64/local/include"     -O2 -Wall  -mtune=core2 -c util.cpp -o util.o util.cpp: In function 'SEXPREC* sourceCpp_50379_vec2matrix2(SEXP, SEXP, SEXP)': util.cpp:75:12: error: 'RTYPE' was not declared in this scope util.cpp:75:17: error: template argument 1 is invalid util.cpp:75:21: error: invalid type in declaration before '=' token util.cpp:75:44: error: could not convert template argument 'RTYPE' to 'int' util.cpp:75:53: error: no matching function for call to 'as(SEXPREC*&)' util.cpp:75:53: note: candidate is: C:/programs/R/current/library/Rcpp/include/Rcpp/as.h:125:29: note: template<class T> T Rcpp::as(SEXP) util.cpp:78:5: error: a template declaration cannot appear at block scope util.cpp:79:5: error: expected ';' before 'return' util.cpp:75:19: warning: unused variable 'x' [-Wunused-variable] util.cpp:76:9: warning: unused variable 'nrow' [-Wunused-variable] util.cpp:77:9: warning: unused variable 'ncol' [-Wunused-variable] make: *** [util.o] Error 1 
Error in Rcpp::sourceCpp("./util.cpp") : 
  Error 1 occurred building shared library.






-----Original Message-----
From: rcpp-devel-bounces at lists.r-forge.r-project.org [mailto:rcpp-devel-bounces at lists.r-forge.r-project.org] On Behalf Of Romain Francois
Sent: 31. maj 2013 11:22
To: rcpp-devel at lists.r-forge.r-project.org
Subject: Re: [Rcpp-devel] Turning a vector into a matrix

Hello Søren,

This is easy templating:

template <int RTYPE>
Matrix<RTYPE> vec2matrix(Vector<RTYPE> x, int nrow, int ncol) {
	return Matrix<RTYPE>(nrow, ncol, x.begin()); }

will work for NumericVector, IntegerVector, CharacterVector, ...

Romain

Le 31/05/13 11:08, Søren Højsgaard a écrit :
> Dear all,
>
> Dirk: Thanks for the reply :).
>
> I shall dare to ask a "bonus question": I've played around with templating so that I get the right output type. I know (thanks to an earlier reply by Romain) how to do so using SEXP's but if I am constructing a utility function to be used on c++ objects, I can't that to work. What I am after should mimic the following such that the output type is determined by the input type:
>
> NumericMatrix vec2matrix(NumericVector x, int nrow, int ncol) {
>    return NumericMatrix(nrow, ncol, x.begin()); }
>
> IntegerMatrix vec2matrix(IntegerVector x, int nrow, int ncol) {
>    return IntegerMatrix(nrow, ncol, x.begin()); }
>
> Any help would be more than welcome.
>
> Best regards
> Søren
>
>
>
>
>
> -----Original Message-----
> From: Dirk Eddelbuettel [mailto:edd at debian.org]
> Sent: 31. maj 2013 03:01
> To: Søren Højsgaard
> Cc: rcpp-devel at r-forge.wu-wien.ac.at
> Subject: Re: [Rcpp-devel] Turning a vector into a matrix
>
>
> Soren,
>
> You missed the most appropriate constructor:
>
>      template <typename Iterator>
>      Matrix( const int& nrows_, const int& ncols, Iterator start ) ;
>
> With that we just do this:
>
>    R> Rcpp::sourceCpp('/tmp/soren.cpp')
>    R> soren(1:4,2,2)
>         [,1] [,2]
>    [1,]    1    3
>    [2,]    2    4
>    R>
>
> and the file soren.cpp is below.
>
> Dirk
>
>
> #include <Rcpp.h>
>
> using namespace Rcpp;
>
> // [[Rcpp::export]]
> NumericMatrix soren(NumericVector x, int n, int k) {
>    return NumericMatrix(n, k, x.begin()); }


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