What is deep learning and why now?

In Chapter 5, Time Series Forecasting as Regression, we talked about machine learning and borrowed a definition from Arthur Samuel: “Machine Learning is a field of study that gives computers the ability to learn without being explicitly programmed.” And we further saw how we can learn useful functions from data using machine learning. Deep learning is a subfield of this same field of study. The objective of deep learning is also to learn useful functions from data, but with a few specifications on how it does that.

Before we talk about what is special about deep learning, let’s answer another question first. Why are we talking about this subfield of machine learning as a separate topic? The answer to that lies in the unreasonable effectiveness of deep learning methods in countless applications. Deep learning has taken the world of machine learning by storm, overthrowing state-of-the-art systems across types of data such as...