[Rcpp-devel] RcppMAtrix<complex> ?

[baptiste auguie]

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 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
>
>