DeepAI.org has a good introduction to the sigmoid function in machine learning. Returning to the Neuron class in Listing 1, beyond the compute() method we have getSum() and getDerivedOutput() .

Modeled on the human brain, neural networks are one of the most common styles of machine learning. ... What an activation function like sigmoid does is bring the output value within -1 and 1, ...

Deep learning's availability of large data and compute power makes it far better than any of the classical machine learning ... function like sigmoid ... learning complex features about an image.