Tutorial on probabilistic topic models

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Over the last decade, probabilistic topic models have emerged as an extremely powerful and popular tool for analyzing large collections of unstructured data. While originally proposed for textual data, topic models have since been applied for various other types of data, such as images, videos, music, social networks and biological data. In this tutorial, I will discuss both the modeling and algorithmic aspects of topic models. I will review the fundamentals of probabilistic generative models, and explain how they can be applied for textual data, starting from simple unigram models to the Latent Dirichlet Allocation model. Then I will look at the problem of learning and inference using topic models, explain why exact inference is intractable for them, review the principle of inference using sampling, and discuss Gibbs Sampling strategies for inference in topic models. As applications of topic models, we will look at semantic search and sentiment analysis. Finally, I will discuss some short-comings of LDA, and briefly touch upon more advanced topic models, such as syntactic, correlated, dynamic and supervised topic models.