[Rcpp-devel] RcppMAtrix<complex> ?

And now, with the new macros (see the thread "[Rcpp-devel] any
preprocessor expert around ?" ), one can write the function as:

#include <RcppArmadillo.h>
using namespace Rcpp ;

RCPP_FUNCTION_2( arma::mat, add_mat,
? ? ? ?arma::mat y, arma::mat x ){

? ? ? ?arma::mat result = x+y;
? ? ? ?return result ;
}

although in this case x and y would be copies of the R data, so it would
be less efficient than your code.

Romain

Le 23/04/10 19:55, Davor Cubranic a ?crit :

Baptiste,

Do have a look at RcppArmadillo, it makes matrix code very easy to write
(and read!). For example, this is a function callable from R to add two
matrices:

#include<RcppArmadillo.h>

using namespace Rcpp;

RcppExport SEXP add_mat(SEXP y_in,
? ? ? ? ? ? ? ? ? ? ? SEXP x_in) {
? ?NumericMatrix y_r(y_in);
? ?arma::mat y(y_r.begin(), y_r.nrow, y_r.ncol(), false);

? ?NumericMatrix x_r(x_in);
? ?arma::mat x(x_r.begin(), x_r.nrow(), x_r.ncol(), false);

? ?arma::mat result = x+y;
? ?return wrap(result);
}

In this case, the matrices are real, not complex. but I believe simply
replacing 'arma::mat' with 'arma::cx_mat' and 'NumericMatrix' with
'ComplexMatrix' will work for the complex case.

Davor


On April 22, 2010 01:22:58 pm baptiste auguie wrote:

OK, thanks for the information. I guess I was lead to believe that
such operations were of common use because I worked previously with
colleagues who had defined their own C++ complex class (and I'm
guessing it was precisely for this purpose of operator overloading).
Sadly the code was not open source. I'll look into armadillo,
hopefully it provides an alternative. I might also need to rethink
what portion of the code I should really be porting out of R; this
function was clearly the bottleneck of my code but it looks like it
will be painful to write it in a lower-level language.

Thanks,

baptiste

On 22 April 2010 18:42, Romain Francois<romain at r-enthusiasts.com>

wrote:

Le 22/04/10 18:19, baptiste auguie a ?crit :

Thanks for the example, it is useful indeed. However, I am having
difficulties with operations involving whole matrices, rather than
matrix elements.

We don't currently have those.

Again I must warn that I don't know C++ ; but the
addition of two matrices does not seem to work out-of-the-box, as
well as more complicated functions. The dispatch of these
functions might not exist for the complex matrix class, or maybe
it is not implemented in Rcpp?

The operations I would need to perform with complex matrices are,

+, -, *, transpose,
as well as operations on 1-column and one-row matrices (==
vectors?) such as exp().

Those are things you'd typically do in R, not in C/C++

Working component by component is not a very attractive option

That is what you usually do in a C/C++ world

so I'm
hoping there is an easy way to define operations between matrices,
matrices and vectors, and matrices and scalars.

One thing you can do perhaps is look into armadillo, which we wrap
nicely with the RcppArmadillo package. and thanks to Doug, the
wrapping is even nicer now since armadillo is packed up inside
RcppArmadillo (but this version is not released yet).

We will not implement these operators soon because it is very easy
to not do it right. armadillo does it nicely.

Thanks,

baptiste

PS: The problem with my previous email was in the gmail vs.
googlemail domain, as Dirk pointed out (I had had that same
problem before, but I forgot!).

On 22 April 2010 13:17, Romain Francois<romain at r-enthusiasts.com>

? wrote:

Thank you for reposting here.

It is not trivial to see what is happening in your example, so
I'll just give you some tools.

The old api (which the classicRcppMatrixExample example uses)
does not have
support for complex vectors or matrices.

The new api does have support for complex vectors and complex
matrices. The
unit test file runit.ComplexVector.R does indeed contain some
very basic examples of using ComplexVector, but not complex
matrices. However, you can
use Rcpp::ComplexMatrix.

Here is an example that calculates the sum of the real part of
the elements
of a complex matrix diagonal and the sum of the imaginary part:

require( Rcpp )
require( inline)

fx<- cfunction( signature( x = "matrix" ), '
? ? ? ? /* grab the R object as a complex matrix */
? ? ? ? ComplexMatrix m(x) ;
? ? ? ? double re_sum = 0.0 ;
? ? ? ? double im_sum = 0.0 ;
? ? ? ? for( int i=0; i<m.ncol(); i++){
? ? ? ? ? ? ? ? re_sum += m(i,i).r ;
? ? ? ? ? ? ? ? im_sum += m(i,i).i ;
? ? ? ? }
? ? ? ? return List::create(
? ? ? ? ? ? ? ? _["sum real part"] = re_sum,
? ? ? ? ? ? ? ? _["sum imag part"] = im_sum
? ? ? ? ? ? ? ? ) ;

', Rcpp = TRUE, includes = "using namespace Rcpp;" )

x<- diag( (1-2i)*1:5 )
fx( x )

Let us know if this gives you enough to get started.

Romain

Le 22/04/10 12:59, baptiste auguie a ?crit :

Dear all,

I'm hoping to port some R code to C++ to make it faster. The
code makes heavy use of matrices of complex numbers, and playing
with the RcppExamples package this morning I got the impression
that it's not currently implemented in Rcpp. I basically took
the example from classicRcppMatrixExample and tried to change
the types from double to complex. I must confess that I don't
know C++, so maybe I missed something obvious.

Attached is my dummy example, as well as the R code I'm trying
to port to give you an idea. Any suggestions would be greatly
appreciated!

Best regards,

baptiste


PS: This message initially failed to reach the list; in the
meantime I got the suggestion from Romain and Dirk to have a
look at the class Rcpp::ComplexMatrix and the example in
runit.ComplexVector.R

--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr

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--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr

|- http://bit.ly/9aKDM9 : embed images in Rd documents
|- http://tr.im/OIXN : raster images and RImageJ
|- http://tr.im/OcQe : Rcpp 0.7.7

--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/9aKDM9 : embed images in Rd documents
|- http://tr.im/OIXN : raster images and RImageJ
|- http://tr.im/OcQe : Rcpp 0.7.7