Accord.Statistics.Kernels.Sparse.SparseGaussian.Distance C# (CSharp) Method

        public override double Distance(double[] x, double[] y)
        {
            if (x == y) 
                return 0.0;

            double norm = SparseLinear.SquaredEuclidean(x, y);

            return 2 - 2 * Math.Exp(-gamma * norm);
        }

        public void DistanceTest()
        {
            Gaussian dense = new Gaussian(3.6);
            SparseGaussian target = new SparseGaussian(3.6);

            double[] sx = { 1, -0.555556, 2, +0.250000, 3, -0.864407, 4, -0.916667 };
            double[] sy = { 1, -0.666667, 2, -0.166667, 3, -0.864407, 4, -0.916667 };
            double[] sz = { 1, -0.944444, 3, -0.898305, 4, -0.916667 };

            double[] dx = { -0.555556, +0.250000, -0.864407, -0.916667 };
            double[] dy = { -0.666667, -0.166667, -0.864407, -0.916667 };
            double[] dz = { -0.944444, +0.000000, -0.898305, -0.916667 };

            double expected, actual;

            expected = dense.Distance(dx, dy);
            actual = target.Distance(sx, sy);
            Assert.AreEqual(expected, actual);

            expected = dense.Distance(dx, dz);
            actual = target.Distance(sx, sz);
            Assert.AreEqual(expected, actual);

            expected = dense.Distance(dy, dz);
            actual = target.Distance(sy, sz);
            Assert.AreEqual(expected, actual);
        }