/*! \pre the \f$ x \f$ and \f$ y \f$ values must be sorted. */
 public BicubicSpline(List <double> xBegin, int size, List <double> yBegin, int ySize, Matrix zData)
 {
     impl_ = new BicubicSplineImpl(xBegin, size, yBegin, ySize, zData);
 }
 /*! \pre the \f$ x \f$ and \f$ y \f$ values must be sorted. */
 public BicubicSpline( List<double> xBegin, int size, List<double> yBegin,int ySize,Matrix zData) 
 {
    impl_ = new BicubicSplineImpl(xBegin, size, yBegin, ySize, zData);
 }