Instead of learning W , Anchor Word algorithms learn the correlations A by again leveraging the separability assumption: , which can be simplified to A = B −1 S * C SS B −1 S * .
the co-occurrence of the anchor words s k and s l transparently captures the correlation between the pair of topics k and l. Note that the anchor words are generally rare words -in order to be the vertices of an underlying convex hull of the word co-occurrence space -whose co-occurrences are even rarer and noisier.