MatrixUtils { public static double frobeniusNorm(DoubleMatrix2D matrix) { return Math.sqrt(matrix.aggregate(Functions.PLUS, Functions.SQUARE)); }  static DoubleMatrix2D normalizeColumnL2(DoubleMatrix2D A, double[] work); static DoubleMatrix2D normalizeSparseColumnL2(
      final DoubleMatrix2D A, final double[] work); static DoubleMatrix2D normalizeColumnL1(DoubleMatrix2D A, double[] work); static double computeOrthogonality(DoubleMatrix2D A); static double computeSparseness(DoubleMatrix2D A); static int[] minInColumns(DoubleMatrix2D A, int[] indices, double[] minValues); static int[] maxInColumns(DoubleMatrix2D A, int[] indices, double[] maxValues); static int[] maxInColumns(
      DoubleMatrix2D A, int[] indices, double[] maxValues, DoubleFunction transform); static int maxInRow(DoubleMatrix2D A, int row); static double[] sumRows(DoubleMatrix2D A, double[] sums); static double frobeniusNorm(DoubleMatrix2D matrix); static DoubleMatrix2D sortedRowsView(
      DoubleMatrix2D matrix, IndirectComparator comparator);  }
@Test public void frobeniusNorm() { assertThat( MatrixUtils.frobeniusNorm( new DenseDoubleMatrix2D( new double[][] { {1, -1}, {2, 0} }))) .isEqualTo(Math.sqrt(1 * 1 + (-1) * (-1) + 2 * 2)); }