Inverse() public method

The Logit mean (activation) function.
The inverse Logit link function is given by g(x) = 1.0 / (1.0 + Math.Exp(-z) in which z = B * x + A.
public Inverse ( double x ) : double
x double A transformed value.
return double
LogitLinkFunction Class Documentation
Exemplo n.º 1
0
        public void LogitLinkFunctionConstructorTest()
        {
            LogitLinkFunction target = new LogitLinkFunction();
            Assert.AreEqual(0, target.A);
            Assert.AreEqual(1, target.B);

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

                Assert.AreEqual(y, target.Function(x), 1e-10);
                Assert.AreEqual(x, target.Inverse(y), 1e-10);
            }
        }
Exemplo n.º 2
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        public void LogitLinkFunctionConstructorTest1()
        {
            double beta = 3.14;
            double constant = 2.91;

            LogitLinkFunction target = new LogitLinkFunction(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 = ((Math.Log(x) - Math.Log(1 - x)) - constant) / beta;

                Assert.AreEqual(y, target.Function(x), 1e-10);
                Assert.AreEqual(x, target.Inverse(y), 1e-10);
            }
        }
Exemplo n.º 3
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        public void DerivativeTest()
        {
            double[] expected =
            {
                0.25, 0.249376, 0.247517, 0.244458, 0.240261, 0.235004,
                0.228784, 0.221713, 0.21391, 0.2055, 0.196612
            };

            LogitLinkFunction target = new LogitLinkFunction();

            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));
            }
        }
Exemplo n.º 4
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        public void DerivativeTest2()
        {
            double beta = 4.2;
            double constant = 0.57;

            double[] expected =
            {
                0.230745, 0.197519, 0.157726, 0.119128, 0.0862579, 
                0.0605722, 0.0416275, 0.0281864, 0.0188941, 0.01258, 0.00833836
            };

            LogitLinkFunction target = new LogitLinkFunction(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));
            }
        }