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Assignment2_answer - Model Answer for Assignment 2 1 Step 1...

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Model Answer for Assignment 2 1 Step 1: Find all the confident rules for a given minimum confidence. ( Given a minimum confidence minconf, a rule is confident if conf( x→c ) ≧ minconf, where conf( x→c ) is the confidence of rule x→c ) Step 2: From association rules to a classifier Let C denote the set of condent rules plus the default rule, Ø c, where c is the majority class in relational table T. Let size(r) denote the number of values in rule r, and let lhs(r) denote the left-hand side of r. We assume that the values in a rule are ordered lexicographically. Similarly, rules can be ordered lexicographically. For example, rule x,y 1 precedes rule y 0 lexicographically. Binary relations: Consider two rules r and r’ in C. We say that r is ranked higher than r’ written as r r’, if the following conditions hold: conf(r) > conf(r’); or if conf(r) = conf(r’), but sup(r) > sup(r’); or if sup(r) = sup(r’), but size(r) < size(r’); or if size(r) = size(r’), but r precedes r’ in the lexicographical order of rules. We say that r is more general than r’ (or r’ is more special than r), written r ’, if lhs(r) lhs(r’). R p G p r CF Principle: If there are choices, the rule of the highest rank has the priority. e can use the MCF principle to resolve the conflict in covering a case: the covering edundant rules: Arule r in C is redundant if there is some rule r’ in C that is more ith only non-redundant rules, we can show that left-hand sides of rules are distinct, tep 3: Pruning the Classifier , the MCF principle implies that the highest ranked d DT: Consider a non-default rule r in C. The parent of r is the rule in C that is more M W rule of a given case is the rule that matches the case and has the highest possible rank. R general and ranked higher than r, that is, r’ p r and r’ p r G R W and thus, that the generalization relationship is a lattice over left-hand sides of rules.
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