Introduction
Following its publication in 2003, Blei et al.’s Latent Dirichlet Allocation (LDA) [3] has made topic modeling – a subfield of machine learning applied to everything from computational linguistics [4] to bioinformatics [8] and political science [2] – one of the most popular and most successful paradigms for both supervised and unsupervised learning.Required Basic Definitions
Joint (combined) probability distribution: In the study of probability, given at least two random variables X, Y, ..., that are defined on a probability space, the joint probability distribution for X, Y, ... is a probability distribution that gives the probability that each of X, Y, ... falls in any particular range or discrete set of values specified for that variable. In the case of only two random variables, this is called a bivariate distribution, but the concept generalizes to any number of random variables, giving a multivariate distribution [Wikipedia].