Encog.Engine.Network.Activation.ActivationLOG.DerivativeFunction C# (CSharp) Method

        public virtual double DerivativeFunction(double b, double a)
        {
            if (b >= 0)
            {
                return 1/(1 + b);
            }
            return 1/(1 - b);
        }

        public void TestLog()
        {
            var activation = new ActivationLOG();
            Assert.IsTrue(activation.HasDerivative());

            var clone = (ActivationLOG) activation.Clone();
            Assert.IsNotNull(clone);

            double[] input = {0.0};

            activation.ActivationFunction(input, 0, 1);

            Assert.AreEqual(0.0, input[0], 0.1);

            // test derivative
            input[0] = activation.DerivativeFunction(input[0],input[0]);
            Assert.AreEqual(1.0, input[0], 0.1);
        }