assoc-rules1-2

assoc-rules1-2 - 1 Association Rules Market Baskets...

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Unformatted text preview: 1 Association Rules Market Baskets Frequent Itemsets A-priori Algorithm 2 The Market-Basket Model r A large set of i t e m s , e.g., things sold in a supermarket. r A large set of b a s k e t s , each of which is a small set of the items, e.g., the things one customer buys on one day. 3 Support r Simplest question: find sets of items that appear frequently in the baskets. r S u p p o r t for itemset I = the number of baskets containing all items in I . r Given a support t h r e s h o l d s , sets of items that appear in > baskets are called f r e q u e n t i t e m s e t s . 4 Example r Items={milk, coke, pepsi, beer, juice}. r Support = 3 baskets. B 1 = {m, c, b} B 2 = {m, p, j} B 3 = {m, b} B 4 = {c, j} B 5 = {m, p, b} B 6 = {m, c, b, j} B 7 = {c, b, j} B 8 = {b, c} r Frequent itemsets: {m}, {c}, {b}, {j}, {m, b}, {c, b}, {j, c}. 5 Applications --- (1) r Real market baskets : chain stores keep terabytes of information about what customers buy together. R Tells how typical customers navigate stores, lets them position tempting items. R Suggests tie-in tricks, e.g., run sale on diapers and raise the price of beer. r High support needed, or no $$s . 6 Applications --- (2) r Baskets = documents; items = words in those documents. R Lets us find words that appear together unusually frequently, i.e., linked concepts. r Baskets = sentences, items = documents containing those sentences. R Items that appear together too often could represent plagiarism. 7 Applications --- (3) r Baskets = Web pages; items = linked pages. R Pairs of pages with many common references may be about the same topic. r Baskets = Web pages p ; items = pages that link to . R Pages with many of the same links may be mirrors or about the same topic. 8 Important Point r Market Baskets is an abstraction that models any many-many relationship between two concepts: items and baskets. baskets....
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This document was uploaded on 03/04/2012.

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assoc-rules1-2 - 1 Association Rules Market Baskets...

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