[Rcpp-devel] Turning a vector into a matrix

[Romain Francois]

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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