  This research proposes a new (old) metric for evaluating goodness of fit in
topic models, the coefficient of determination, or $R^2$. Within the context of
topic modeling, $R^2$ has the same interpretation that it does when used in a
broader class of statistical models. Reporting $R^2$ with topic models
addresses two current problems in topic modeling: a lack of standard
cross-contextual evaluation metrics for topic modeling and ease of
communication with lay audiences. The author proposes that $R^2$ should be
reported as a standard metric when constructing topic models.
