# Chapter 27. Regression

Regression is a logical extension of classification. Rather than just predicting a single value from a set of values, regression is the act of predicting a real number (or continuous variable) from a set of features (represented as numbers).

Regression can be harder than classification because, from a mathematical perspective, there are an infinite number of possible output values. Furthermore, we aim to optimize some metric of error between the predicted and true value, as opposed to an accuracy rate. Aside from that, regression and classification are fairly similar. For this reason, we will see a lot of the same underlying concepts applied to regression as we did with classification.

# Use Cases

The following is a small set of regression use cases that can get you thinking about potential regression problems in your own domain:

Predicting movie viewership

Given information about a movie and the movie-going public, such as how many people have watched the trailer or shared it on social media, you might want to predict how many people are likely to watch the movie when it comes out.

Predicting company revenue

Given a current growth trajectory, the market, and seasonality, you might want to predict how much revenue a company will gain in the future.

Predicting crop yield

Given information about the particular area in which a crop is grown, as well as the current weather throughout the year, you might want to predict the total crop yield for a particular ...

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