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Published byEmil Gilmore Modified over 9 years ago
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CURE Clustering Using Representatives Handles outliers well. Hierarchical, partition First a constant number of points c, are chosen from each cluster. These well scattered points are then shrunk towards the cluster’s centroid by applying a shrinkage factor alpha(α). Use many points to represent a cluster instead of only one Points will be well scattered. CURE then uses the hierarchical algorithm Limited main memory.
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CURE Approach
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CURE Algorithm
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CURE for Large Databases
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Comparison of Clustering Techniques
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Association Rule are used to shoe the relationship between data items. Application : retail stores, marketing, advertisement, floor placement, inventory control.
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Example: Market Basket Data Items frequently purchased together: Bread PeanutButter Uses: Placement Advertising Sales Coupons Objective: increase sales and reduce costs
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Association Rule Definitions Set of items: I={I 1,I 2,…,I m } Transactions: D={t 1,t 2, …, t n }, t j I Itemset: {I i1,I i2, …, I ik } I Support of an itemset: Percentage of transactions which contain that itemset. Large (Frequent) itemset: Itemset whose number of occurrences is above a threshold.
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Association Rules Example I = { Beer, Bread, Jelly, Milk, PeanutButter} Support of {Bread,PeanutButter} is 60%
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Association Rule Definitions Given a set of items I={I 1,I 2,…,I m } and a database of transactions D={t 1,t 2, …, t n } where t i ={I i1,I i2, …, I ik } and I ij I, Association Rule (AR): implication X Y where X,Y I and X Y = ; Support of AR (s) X Y: Percentage of transactions that contain X Y Confidence of AR ( ) X Y: Ratio of number of transactions that contain X Y to the number that contain X.
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Association Rules Ex (cont’d)
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Association Rule Problem Given a set of items I={I 1,I 2,…,I m } and a database of transactions D={t 1,t 2, …, t n } where t i ={I i1,I i2, …, I ik } and I ij I, the Association Rule Problem is to identify all association rules X Y with a minimum support and confidence. Link Analysis NOTE: Support of X Y is same as support of X Y.
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Large Itemsets To finding association Rule : 1. Find Large Itemsets. 2. Generate rules from frequent itemsets. An itemset is any subset of the set of all items.
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Algorithm to Generate ARs
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Apriori Large Itemset Property: Any subset of a large itemset is large. Contrapositive: If an itemset is not large, none of its supersets are large.
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Large Itemset Property
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