[Rcpp-devel] Matrix columns

[Michael Braun]

Nick:

I had a similar problem a few weeks ago.  The underscore is part of the Rcpp namespace.  So I added using namespace Rcpp at the beginning of my function, and then all worked well.  I can't tell from the compiler output if that is *exactly* what the problem is, but it's worth taking a look.

Michael




On May 14, 2011, at 5:33 PM, <rcpp-devel-request at r-forge.wu-wien.ac.at> <rcpp-devel-request at r-forge.wu-wien.ac.at> wrote:

> 
> Message: 5
> Date: Sat, 14 May 2011 23:12:08 +0200
> From: "Nick Sabbe" <nick.sabbe at ugent.be>
> Subject: [Rcpp-devel] Matrix columns
> To: <rcpp-devel at lists.r-forge.r-project.org>
> Message-ID: <02a301cc127b$95e964c0$c1bc2e40$@sabbe at ugent.be>
> Content-Type: text/plain; charset="us-ascii"
> 
> Hi all,
> 
> 
> 
> I've been trying the following, with the main part ripped from
> rcpp-quickref:
> 
>    SEXP dfr2Mat(SEXP dfr)
> 
>    {
> 
>        DataFrame df = dfr;
> 
>        int* dm = INTEGER( ::Rf_getAttrib( df, R_DimSymbol ) ) ;
> 
>        int rows = dm[0];
> 
>        int cols = dm[1];
> 
>        NumericMatrix retMat (rows, cols);
> 
>        for(int i = 0; i < cols; i++)
> 
>        {
> 
>            NumericVector curcol = df(i);
> 
>            //NumericMatrix::Column zzcol = xx( _, 1);
> 
>            NumericMatrix::Column cl = retMat.( _, i);
> 
>            cl = curcol;
> 
>        }
> 
>        return retMat;
> 
>    }
> 
> When compiling this, I get some errors starting from the line after the
> comment (i.e. line 64):
> 
> 
> 
> main.cpp: In function 'SEXPREC* dfr2Mat(SEXPREC*)':
> 
> main.cpp:64: error: invalid conversion from 'SEXPREC*' to 'int'
> 
> main.cpp:64: error:   initializing argument 1 of 'typename
> Rcpp::Vector<RTYPE>::Proxy Rcpp::Matrix<RTYPE>::operator()(int, int) [with
> int RTYPE = 14]'
> 
> main.cpp:64: error: conversion from 'double' to non-scalar type
> 'Rcpp::MatrixColumn<14>' requested
> 
> main.cpp:65: error: no match for 'operator=' in 'cl = curcol'
> 
> C:/Users/nisabbe/Documents/R/win-library/2.11/Rcpp/include/Rcpp/vector/Matri
> xColumn.h:40: note: candidates are: Rcpp::MatrixColumn<RTYPE>&
> Rcpp::MatrixColumn<RTYPE>::operator=(Rcpp::MatrixColumn<RTYPE>&) [with int
> RTYPE = 14]
> 
> 
> 
> I suspect it has something to do with this underscore syntax.
> 
> I compiled with the following statement:
> 
> g++ -I"C:/PROGRA~1/R/R-211~1.1/include"
> -I"C:/Users/nisabbe/Documents/R/win-library/2.11/Rcpp/include" -O2 -Wall -c
> main.cpp -o main.o
> 
> And the version of rcpp I installed is 0.9.4 on the most recent version of
> R.
> 
> 
> 
> Can anyone show me what is wrong here?
> 
> Besides the syntax problems, what I am doing here should work, right?
> 
> I know there are non-Rcpp ways to get this done, but this is just something
> to get me started.
> 
> 
> 
> And as an addendum: where can I find out how (not) to use this underscore?
> 
> 
> 
> Nick Sabbe
> 
> --
> 
> ping: nick.sabbe at ugent.be
> 
> link:  <http://biomath.ugent.be/> http://biomath.ugent.be
> 
> wink: A1.056, Coupure Links 653, 9000 Gent
> 
> ring: 09/264.59.36
> 
> 

-------------------------------------------
Michael Braun
Associate Professor of Management Science (Marketing Group)
MIT Sloan School of Management
100 Main St.., E62-535
Cambridge, MA 02139
braunm at mit.edu
617-253-3436