If you have used any online shopping system in the last 10 years, you have probably seen recommendations. Some are like Amazon's, customers who bought X also bought Y, feature. These will be discussed in the Basket analysis section. Other recommendations are based on predicting the rating of a product, such as a movie.
The problem of learning recommendations based on past product ratings was made famous by the Netflix prize, a million-dollar machine-learning public challenge by Netflix. Netflix is a movie-streaming company. One of the distinguishing features of the service is that it gives users the option to rate the films they have seen. Netflix then uses these ratings to recommend other films to its customers. In this machine-learning problem, you not only have the information about which films the user saw, but also about how the...
