Negative and Rare Patterns Rare patterns: Very low support but interesting E.g. buying Rolex watches Mining: Setting individual-based or special group-based support threshold for valuable items Negative patterns Since it is unlikely that one buys ford expedition (an SUV car )and Toyota Prius (a hybrid car together, Ford Expedition and Toyota Prius are likely negatively correlated patterns Negatively correlated patterns that are infrequent tend to be more interesting than those that are frequent13 Negative and Rare Patterns ◼ Rare patterns: Very low support but interesting ◼ E.g., buying Rolex watches ◼ Mining: Setting individual-based or special group-based support threshold for valuable items ◼ Negative patterns ◼ Since it is unlikely that one buys Ford Expedition (an SUV car) and Toyota Prius (a hybrid car) together, Ford Expedition and Toyota Prius are likely negatively correlated patterns ◼ Negatively correlated patterns that are infrequent tend to be more interesting than those that are frequent