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. 2014 Aug 1;9(8):e103408. doi: 10.1371/journal.pone.0103408

Figure 1. The graphical model and generative story for ATAM.

Figure 1

The graphical model representation of ATAM using plate notation, followed by the “generative story” description of the model. In the graphical model, the variable z denotes the topic index, and the Bernoulli variables x and ℓ are switch variables indicating whether a word is an ailment or topic word and whether a word is background noise. These three variables do not appear in the conditional likelihood because they have been summed out. A is the number of ailments, Y is the number of aspects, Z is the number of topics, D is the number of documents, and Nm is the number of tokens in document m. In the generative description, “Dir” refers to the Dirichlet distribution.