docs: public static void abs(DMatrixD1 a , DMatrixD1 c ) {
          c.reshape(a.numRows,a.numCols);
  
          final int length = a.getNumElements();
  
          for ( int i = 0; i < length; i++ ) {
              c.data[i] = Math.abs(a.data[i]);
          }
      }