Mixture Models and Frequent Sets: Combining Global and Local Methods for 0-1 Data.

We study the interaction between global and local techniques in data mining. Specifically, we study the collections of frequent sets in clusters produced by a probabilistic clustering using mixtures of Bernoulli models. That is, we first analyze 0--1 datasets by a global technique (probabilistic clustering using the EM algorithm) and then do a local analysis (discovery of frequent sets) in each of the clusters. The results indicate that the use of clustering as a preliminary phase in finding frequent sets produces clusters that have significantly di#erent collections of frequent sets. We also test the significance of the di#erences in the frequent set collections in the di#erent clusters by obtaining estimates of the underlying joint density. To get from the local patterns in each cluster back to distributions, we use the maximum entropy technique [17] to obtain a local model for each cluster, and then combine these local models to get a mixture model. We obtain clear improvements to the approximation quality against the use of either the mixture model or the maximum entropy model