[Rcpp-devel] Is there an Rcpp class for arrays with > 2 dimensions?

[Douglas Bates]

On Tue, Jun 15, 2010 at 2:11 PM, Romain Francois
<romain at r-enthusiasts.com> wrote:
>
> Le 15/06/10 20:45, Dominick Samperi a écrit :
>>
>> I have tried something like
>>
>> Rcpp::NumericVector nm(Rcpp::Dimension(2,3,4));
>
> I get this:
>
>> require( Rcpp )
> Le chargement a nécessité le package : Rcpp
>> require( inline )
> Le chargement a nécessité le package : inline
>> fx <- cxxfunction( signature(), ' return NumericVector( Dimension(2,3,4) )
>> ;', plugin = "Rcpp" )
>>
>> fx()
> , , 1
>
>     [,1] [,2] [,3]
> [1,]    0    0    0
> [2,]    0    0    0
>
> , , 2
>
>     [,1] [,2] [,3]
> [1,]    0    0    0
> [2,]    0    0    0
>
> , , 3
>
>     [,1] [,2] [,3]
> [1,]    0    0    0
> [2,]    0    0    0
>
> , , 4
>
>     [,1] [,2] [,3]
> [1,]    0    0    0
> [2,]    0    0    0
>
> which looks about right. although not much useful without some more support
> such as extract or set the values.

Actually, that was what I was thinking of.   All I want to do is to
generate the array and then I will fill in the values using a pointer.

>> But there seems to be a problem due to non-public fields.
>
> What do you mean ?
>
>> Am I misunderstanding the purpose of Dimension() here?
>
> Perhaps. Perhaps not. You did not tell us what you understand.
>
>> On Tue, Jun 15, 2010 at 2:19 PM, Romain Francois
>> <romain at r-enthusiasts.com <mailto:romain at r-enthusiasts.com>> wrote:
>>
>>    Le 15/06/10 20:08, Douglas Bates a écrit :
>>
>>
>>        I may be confusing Armadillo classes and Rcpp classes but I seem to
>>        recall that there is an Rcpp class for arrays with more than 2
>>        dimensions.  However, I can't find anything that looks like that in
>>        the declarations or in the unit tests.  I can easily create such an
>>        object by installing a dim attribute on a Vector type but I didn't
>>        want to reinvent the wheel.
>>
>>        Is there such a class or am I misremembering?
>>
>>
>>    We do not have invented that wheel. It should not be too hard to
>>    generalize what we do with Rcpp::Matrix
>>
>>    You can ignore the member functions that have diag in their names.
>>
>>    although, we would probably also have to extend the
>>    Vector::operator() for more dimensions, and probably also
>>    Vector::offset.
>>
>>    I feel somewhat lazy here, but if you or someone else decides to
>>    pick it up, I will have a look.
>>
>>    Romain
>
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