[R] Problem with .C

[Uwe Ligges]

On 06.10.2011 14:51, Jan van der Laan wrote:
> An obvious reason might be that your second argument should be a pointer
> to int.
>
> As others have mentioned, you might want to have a look at Rccp and/or
> inline. The documentation is good and I find it much easier to work with.
>
> For example, your example could be written as:
>
> library(Rcpp)
> library(inline)
>
> test <- cxxfunction(signature(x = "numeric" ) , '
> Rcpp::NumericVector v(x);
> Rcpp::NumericVector result(v.length());
> for (int i = 0; i < v.length(); ++i) {
> result[i] = v[i] + i;
> }
> return(result);
> ', plugin = "Rcpp" )
>


Oh, come on, this is now really too much of overkill.

Just make the original source


void test(double *b, int *l)
{
      int i;
      for(i=0; i < *l ; i++) b[i] += i;
}


which you would have know after reading the Wriiting R Extensions manual.

Best,
Uwe Ligges




> HTH,
>
> Jan
>
>
> Quoting Grigory Alexandrovich <alexandrovich at mathematik.uni-marburg.de>:
>
>> Hello,
>>
>> first thank you for your answers.
>>
>> I did not read the whole pdf Writing R Extension, but I read this
>> strongly shortened introduction to this subject:
>>
>> http://www.math.kit.edu/stoch/~lindner/media/.c.call%20extensions.pdf
>>
>> I get the same error with this C-function:
>>
>> void test(double * b, int l)
>> {
>> int i;
>> for(i=0; i < l ; i++) b[i] +=i;
>> }
>>
>>
>>
>> I call it from R like this:
>>
>> parameter = c(0,0,1,1,1,0,1.5,0.7,0,1.2,0.3);
>> .C("test", as.double(parameter), as.integer(11))
>>
>> The programm crashes even in this simple case.
>> Where can be the error?
>>
>> Thanks
>> Grigory Alexandrovich
>>
>>
>>
>>
>>
>>
>>
>> Answer 1
>>> Without knowing that C code, we cannot know. Have you read Writing R
>>> Extensions carefully? I.e. take care with memory allocation and
>>> printing as mentioned in the manual.
>>>
>>> Uwe Ligges
>>
>>
>> Answer 2
>>> This looks like a classic case of not reading the manual, and then
>>> compounding it by not reading the posting guide. The manual would be
>>> the "Writing R Extensions" pdf that comes with R or you can google
>>> it. The posting guide is referenced at the bottom of this and every
>>> other posting on this mailing list.
>>> There are nearly an infinite variety of errors that can lead to a
>>> "crash", so it is really unreasonable of you to pose this question
>>> this way and expect constructive assistance.
>>> ---------------------------------------------------------------------------
>>>
>>> Jeff Newmiller The ..... ..... Go Live...
>>> DCN:<jdnewmil at dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go...
>>> Live: OO#.. Dead: OO#.. Playing
>>> Research Engineer (Solar/Batteries O.O#. #.O#. with
>>> /Software/Embedded Controllers) .OO#. .OO#. rocks...1k
>>> ---------------------------------------------------------------------------
>>>
>>> Sent from my phone. Please excuse my brevity.
>>
>>
>> Answer 3
>>
>>> It's impossible to say, with such minimal information, but a reasonable
>>> guess is that there is a problem with the declaration of "x" and "y" in
>>> foo.c. These would (I think) need to be declared as double *, not
>>> double,
>>> when foo is called from .C().
>>>
>>> cheers,
>>>
>>> Rolf Turner
>>
>>
>> Answer 4
>>
>>> Hi,
>>>
>>> As other have said, it's very difficult to help you without an example
>>> + code to know what you are talking about.
>>>
>>> That having been said, it seems as if you are just getting your feet
>>> wet in this R <--> C bridge, and I'd recommend you checkout the "Rcpp"
>>> and "inline" package to help make your life a lot easier ...
>>>
>>> -steve
>>
>>
>>
>>
>>
>>
>>
>>
>>> On 04.10.2011 14:04, Grigory Alexandrovich wrote:
>>>> Hello,
>>>>
>>>> I wrote a function in C, which works fine if called from the
>>>> main-function in C.
>>>>
>>>> But as soon as I try to call this function from R like .C('foo',
>>>> as.double(x), as.integer(y)), the programm crashes.
>>>>
>>>> I created a dll with the cmd command R --arch x64 CMD SHLIB foo.c and
>>>> loaded it into R with dyn.load().
>>>>
>>>> What can be the cause of such behaviour?
>>>> Again, the C-funcion itself works, but not if called from R.
>>>>
>>>> Thanks
>>>> Grigory Alexandrovich
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
>