Welcome to matrix factorization and advanced techniques, the fourth course in our specialization on recommender systems. The idea of matrix factorization starts with the concept of dimensionality reduction. When we think about a ratings matrix and we think about having millions or hundreds of millions of users and thousands, or hundreds of thousands, or millions of products, what we have is a highly specialized representation. And frankly an overly detailed representation of taste. What do people like? And what do they like in products? The whole idea of the techniques were studying in this course is to find a way to compress that representation and distill out whether there were some essential and important dimensions of taste. That if we can represent, we can simplify the whole process of recommendation into identifying a person's taste and identifying how each individual product matches against taste space. Now this gives us the promise of efficiency and higher quality. This is one of those cases were compressing and losing a little bit of data, helps us get over artifacts and get to a smoother and more realistic rendering of people's taste. So, in this course, we're going to be looking at exploiting the best of machine learning. Machine learning techniques have been doing a lot to look at dimensionality reduction and at how we can, not only take a look at taste as a function of ratings, but take the both end approach of weaving in whatever we know about user properties like demographics, item properties like content, even contextual properties, all into a model that represents taste as compactly as possible, to give us the most effective recommendations possible. >> The key concepts of this course start with matrix factorization for collaborative filtering, where we'll learn how to break the ratings matrix down into smaller matrices that describe user preference for different types of items or characteristics of items, and the extent to which items express those characteristics. Through this, we'll also start to look at machine learning and optimization approaches to recommender systems, where we directly learn our recommender that minimizes some error or maximizes some kind of utility function. We'll then move in to hybrid algorithms which look at combining multiple algorithms into one, so you could combine a collaborative filter and a content based filter for example. To allow their strength to compliment each other and build a better recommendation than either one can compute alone. These types of recommenders are very widely used in practice. We'll then look at learning-to-rank which looks at what happens if we skip this whole prediction thing entirely? And directly optimize our recommender for producing good top end lists. And finally we will talk about number of advanced topics such as context to where recommendation, aspects, and issues of deploying recommenders at scale on industrial applications and several addition topics. >> This course is structured around three major topics. Weeks one and two focus on matrix factorization. There will be a spreadsheet assignment that builds upon matrix factorization. And for the honors track a programming assignment plus a quiz. Week three will focus on hybrid algorithms, which will also have a spreadsheet assignment and a quiz. And week four will look at advanced techniques and topics, where there will be an honors assignment programmed in LensKit as well as the final quiz of this course and of this specialization. Let's move forward into matrix factorization.