    @Test
    public void concat1d() {

        double[] y1 = { 1.0, 2.0, 3.0 };
        double[] y2 = { 4.0, 5.0 };
        double[] y = RelevanceModel.concat(y1, y2);
        double[] expected = { 1.0, 2.0, 3.0, 4.0, 5.0 };
        assertTrue(Arrays.equals(y, expected));
    }