Visualizing association rules with interactive mosaic plots

Association rules are amongst the most important patterns that can be discovered using data mining. Their automatic discovery is supported by most, if not all, data mining software tools. Moreover, many techniques have been devised to lter the most interesting (in many senses) rules from the complete set of discovered rules, such that the users are not swamped by results. However, association rules are actually hard to understand; even more so if one only looks at the most interesting rules. For example, rather strong correlations between attributes are not always obvious from the discovered rules. Similarly, a deeper explanation of related association rules may be missing from the rule set. In this paper we show how Mosaic plots and, especially, their variant called Double Decker plots, can be used to visualize association rules. These plots visualize the contingency table that yields the association rule as well as the other potential rules in that table, whether they meet the thresholds or not. This gives a deeper understanding on the nature of the correlation between the left-hand side of the rule and the right-hand side. Moreover, we show how an interactive use of these plots helps the user to understand the relationship between related association rules.