[Rcpp-devel] RcppMAtrix<complex> ?

[Romain Francois]

Le 22/04/10 18:19, baptiste auguie a écrit :
> 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 écrit :
>>>
>>> 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
>> |- 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