What Is Sigmoid Function?

The sigmoid function is a mathematical function that takes in any input, a, and returns a value between 0 and 1. It is defined as:

sigmoid(a) = 1 / (1 + e^(-a))

where e is the base of the natural logarithm. The sigmoid function has a “S” shaped curve, and is often used in machine learning as an activation function for neural networks. It has a number of useful properties, including being differentiable, which makes it useful for training neural networks using gradient descent.