.Call - applying setAttrib(x, R_DimSymbol, s) to a matrix being an element of a list

Dear Simon,

you gave us only a fragment of your code, so I can only guess what the 

problem is:

What is imgSize? The behavior you describe seems as if you re-using the 

imgSize SEXP in all elements.

AFAIR in your case setAttrib doesn't copy the value, so you need to do so 

yourself (or alloc new dim array

for each element).

Sorry, it is always a tradeoff - either to explain or put a relatively large 
code, which also uses non-standard libraries making the code difficult to 
read. imgSize values are reset in between: see the full code below. The SEXP 
pointer imgSize stays in tact, that's true, but its values are changed (the 
problem is, they are always the last in the row). I.e. if I have 3 images 
40x20, 200x100 and 150x75 I will get three matrices of 150x75, but if I omit 
setAtrib and return vectors I get vectors of different length.

Oleg

SEXP load2DImages(SEXP fileNames) {
  int nFiles = LENGTH(fileNames);
  std::cout << "Loading " << nFiles << " files..." << std::endl;
  // SEXP result = allocList(nFiles);
  SEXP result = allocVector(VECSXP, nFiles);
  PROTECT(result);
  SEXP imgSize = allocVector(INTSXP, 2);
  PROTECT(imgSize);
  TRGB2DImage::Pointer image;
  TRGB2DReader::Pointer reader = TRGB2DReader::New();
  TRGB2DImage::SizeType size;      TRGB2DImage::IndexType pixIndex;
  for (int i = 0; i < nFiles; i++) {
      try {
          char *filename = CHAR(asChar(VECTOR_ELT(fileNames, i)));
          std::cout << std::endl << "Loading image file " << filename << 
"... ";
          reader->SetFileName(filename);
          reader->Update();
          image = reader->GetOutput();
      } catch(...) {
          std::cout << "failed!";
          continue;
      }
      std::cout << std::endl;
      size = image->GetLargestPossibleRegion().GetSize();
      INTEGER(imgSize)[0] = size[1];
      INTEGER(imgSize)[1] = size[0];
      std::cout << size[0] << " x " << size[1] << std::endl;
      SET_VECTOR_ELT(result, i, allocVector(INTSXP, size[0] * size[1]));
      SEXP element = VECTOR_ELT(result, i);
      for (int ix = 0; ix < size[0]; ix++) {
          pixIndex[0] = ix;
          for (int iy = 0; iy < size[1]; iy++) {
              pixIndex[1] = iy;
              INTEGER(element)[size[1] * ix + iy] = 
getIntRGBColour(image->GetPixel(pixIndex));
          }
      }
      setAttrib(element, R_DimSymbol, imgSize);
  }
  UNPROTECT(2);
  if (nFiles == 1)
      return VECTOR_ELT(result, 0);
  else
      return result;
}

Dr Oleg Sklyar
European Bioinformatics Institute
Wellcome Trust Genome Campus
Hinxton, Cambridge, CB10 1SD
England
phone/fax  +44(0)1223 49 4478/4468
e-mail osklyar@ebi.ac.uk



Simon Urbanek wrote:

Oleg,

you gave us only a fragment of your code, so I can only guess what the 
problem is:

On Mar 16, 2005, at 12:40 PM, Oleg Sklyar wrote:

// converting element into a matrix
setAttrib(element, R_DimSymbol, imgSize);

What is imgSize? The behavior you describe seems as if you re-using the 
imgSize SEXP in all elements. AFAIR in your case setAttrib doesn't copy the 
value, so you need to do so yourself (or alloc new dim array for each 
element).

Cheers,
Simon