Activation function

Introduction

In machine learning, an activation function is a mathematical function applied to the output of a neuron in a neural network. The activation function determines the output of the neuron based on its input, and is a key component of the neural network architecture.

What is an Activation Function?

An activation function is a non-linear function that is applied to the weighted sum of the inputs to a neuron. The activation function maps the input to a non-linear output, which is used as the input to the next layer of neurons.

There are many types of activation functions used in neural networks, including sigmoid, tanh, ReLU (rectified linear unit), and softmax. The choice of activation function depends on the specific problem being solved and the architecture of the neural network.

The activation function is a critical component of a neural network because it introduces non-linearity into the model, allowing the network to model complex relationships between the input and output.

Why are Activation Functions Used?

Activation functions are used in neural networks to introduce non-linearity into the model. Without an activation function, the output of a neural network would be a linear combination of the inputs, which is not capable of modeling complex relationships between the input and output.

The activation function allows the neural network to model non-linear relationships between the input and output, making it more powerful and expressive. It also helps to prevent the vanishing gradient problem, which can occur when training deep neural networks.

Types of Activation Functions

There are many types of activation functions used in neural networks, including:

Sigmoid

The sigmoid function is a popular activation function that maps any input value to a value between 0 and 1. The sigmoid function is useful for binary classification problems, where the output is either 0 or 1.

Tanh

The tanh function is a hyperbolic tangent function that maps any input value to a value between -1 and 1. The tanh function is useful for regression problems, where the output can take on a continuous range of values.

ReLU

The rectified linear unit (ReLU) function is a popular activation function that maps any input value to either 0 or the input value itself. The ReLU function is useful for deep neural networks, where it can help to prevent the vanishing gradient problem.

Softmax

The softmax function is a popular activation function that is used in the output layer of a neural network for multi-class classification problems. The softmax function maps the input to a probability distribution over the output classes.

Explain Like I'm 5 (ELI5)

Activation functions are like special glasses that help a computer to see better. They help the computer understand pictures, sounds, or other things by making them look different, like changing the color or making them brighter or darker. This makes it easier for the computer to know what the picture or sound is and what to do with it. Different glasses are used for different things, like seeing colors or finding the loudest sound.