docs: public void set( int index , double value ) {
          if( mat.getType() == MatrixType.DDRM ) {
              ((DMatrixRMaj) mat).set(index, value);
          } else if( mat.getType() == MatrixType.FDRM ) {
              ((FMatrixRMaj) mat).set(index, (float)value);
          } else {
              throw new RuntimeException("Not supported yet for this matrix type");
          }
      }