Accord.Statistics.Kernels.Cauchy.Function C# (CSharp) Method

        public override double Function(double[] x, double[] y)
        {
            // Optimization in case x and y are
            // exactly the same object reference.

            if (x == y)
                return 1.0;

            double norm = 0.0;
            for (int i = 0; i < x.Length; i++)
            {
                double d = x[i] - y[i];
                norm += d * d;
            }

            return (1.0 / (1.0 + norm / sigma));
        }

        public void FunctionTest()
        {
            Cauchy dense = new Cauchy(3.6);
            SparseCauchy target = new SparseCauchy(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.Function(dx, dy);
            actual = target.Function(sx, sy);
            Assert.AreEqual(expected, actual);

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

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