Types of Machine Learning

Depending on the application and what data is available, there are different types of machine learning algorithms to choose from. I’ll briefly cover each of the following.

Supervised Learning

Supervised learning allows us to make predictions using correctly labeled data. Labeled data is a group of examples that has informative tags or outputs. For example, photos with associated hashtags or a house’s features (eq. number of bedrooms, location) and its price.

By using supervised learning we can fit a line to the labelled data that either splits the data into categories or represents the trend of the data. Using this line we are able to make predictions on new data. For example, we can look at new photos and predict hashtags or look at a new house’s features and predict its price.

If the output we are trying to predict is a list of tags or values we call it classification. If the output we are trying to predict is a number we call it regression.

Unsupervised Learning

Unsupervised learning is helpful when we have unlabeled data or we are not exactly sure what outputs (like an image’s hashtags or a house’s price) are meaningful. Instead we can identify patterns among unlabeled data. For example, we can identify related items on an e-commerce website or recommend items to someone based on others who made similar purchases.

If the pattern is a group we call it a cluster. If the pattern is a rule (e.q. if this, then that) we call it an association.

Reinforcement Learning

Reinforcement learning doesn’t use an existing data set. Instead we create an agent to collect its own data through trial-and-error in an environment where it is reinforced with a reward. For example, an agent can learn to play Mario by receiving a positive reward for collecting coins and a negative reward for walking into a Goomba.

Reinforcement learning is inspired by the way that humans learn and has turned out to be an effective way to teach computers. Specifically, reinforcement has been effective at training computers to play games like Go and Dota.