Hello,
I tried again, and now it works fine.

Qt Code:
  1. class Q2DDoubleVector : public QVector< QVector<double> > // Overloading Class QVector to allow for 2 dimensional vectors.
  2. {
  3. public:
  4. // constructor
  5. Q2DDoubleVector() : QVector< QVector<double> >(){}
  6. // methods
  7. // matrix resize
  8. void mresize(int rows, int columns);
  9. // destructor
  10. virtual ~Q2DDoubleVector() {}
  11. };
  12.  
  13. void Q2DDoubleVector::mresize(int rows, int columns)
  14. {
  15. this->resize(rows);
  16. for(int r=0; r<rows; r++) {
  17. (*this)[r].resize(columns);
  18. }
  19. }
  20.  
  21. Q2DDoubleVector matrix;
  22. matrix.mresize(ROWS, COLS);
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Thank's a lot for your help!

Uwe Fechner