public void DerivativeTest()
        {
            double beta     = 3.14;
            double constant = 2.91;

            double[] expected =
            {
                -0.370803, -0.302092,  -0.25085, -0.21162,  -0.180922,
                -0.156449, -0.136626, -0.120345, -0.10681, -0.0954358, -0.0857865
            };

            InverseLinkFunction target = new InverseLinkFunction(beta, constant);

            for (int i = 0; i < 11; i++)
            {
                double x = i / 10.0;
                double y = target.Inverse(x);

                double d1 = target.Derivative(x);
                double d2 = target.Derivative2(y);

                Assert.AreEqual(expected[i], d1, 1e-6);
                Assert.AreEqual(expected[i], d2, 1e-6);

                Assert.IsFalse(Double.IsNaN(d1));
                Assert.IsFalse(Double.IsNaN(d2));
            }
        }
        public void InverseLinkFunctionConstructorTest()
        {
            InverseLinkFunction target = new InverseLinkFunction();

            Assert.AreEqual(0, target.A);
            Assert.AreEqual(1, target.B);

            for (int i = 0; i < 11; i++)
            {
                double x = i / 10.0;
                double y = 1 / x;

                Assert.AreEqual(y, target.Function(x), 1e-10);
                Assert.AreEqual(x, target.Inverse(y), 1e-10);
            }
        }
        public void InverseLinkFunctionConstructorTest1()
        {
            double beta     = 3.14;
            double constant = 2.91;

            InverseLinkFunction target = new InverseLinkFunction(beta, constant);

            Assert.AreEqual(constant, target.A);
            Assert.AreEqual(beta, target.B);

            for (int i = 0; i < 11; i++)
            {
                double x = i / 10.0;
                double y = (1 / x - constant) / beta;

                Assert.AreEqual(y, target.Function(x), 1e-10);
                Assert.AreEqual(x, target.Inverse(y), 1e-10);
            }
        }