code: public static RealMatrix getRowRange (RealMatrix matrix, int start, int end) {
          return matrix.getSubMatrix(start, end, 0, matrix.getColumnDimension() - 1);
      }
docs: Returns the row range from the matrix as a new matrix.
  
  @param matrix The input matrix
  @param start The index of the row to start with (inclusive)
  @param end The index of the row to end with (inclusive)
  @return A new matrix with rows specified