public void InverseSquaredLinkFunctionConstructorTest()
        {
            InverseSquaredLinkFunction target = new InverseSquaredLinkFunction();
            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 * x);

                Assert.AreEqual(y, target.Function(x), 1e-10);
                Assert.AreEqual(x, target.Inverse(y), 1e-10);
            }
        }
        public void InverseSquaredLinkFunctionConstructorTest1()
        {
            double beta = 3.14;
            double constant = 2.91;

            InverseSquaredLinkFunction target = new InverseSquaredLinkFunction(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 * x) - constant) / beta;

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

            double[] expected =
            {
                -0.316272, -0.271211, -0.235919, -0.207668, -0.184638,
                -0.16557, -0.149573, -0.135995, -0.124354, -0.114284, -0.105503
            };

            InverseSquaredLinkFunction target = new InverseSquaredLinkFunction(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));
            }
        }