dm3part2 - University of Florida CISE department...

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University of Florida CISE department Gator Engineering Classification Part 2 Dr. Sanjay Ranka Professor Computer and Information Science and Engineering University of Florida, Gainesville
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Overview • Rule based Classifiers • Nearest-neighbor Classifiers
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Rule Based Classifiers • Classify instances by using a collection of “if … then …” rules • Rules are presented in Disjunctive Normal Form, R = (r 1 v r 2 v … r k ) R is called rule set r i ’s are called classification rules • Each classification rule is of form r i : (Condition i ) y •Condition is a conjunction of attribute tests y is the class label
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Rule Based Classifiers r i : (Condition i ) y – LHS of the rule is called rule antecedent or pre-condition – RHS is called the rule consequent • If the attributes of an instance satisfy the pre- condition of a rule, then the instance is assigned to the class designated by the rule consequent • Example – (Blood Type=Warm) (Lay Eggs=Yes) Birds – (Taxable Income < 50K) (Refund=Yes) Cheat=No
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Classifying Instances with Rules • A rule r covers an instance x if the attributes of the instance satisfy the condition of the rule • Rule: r : (Age < 35) (Status = Married) Cheat=No • Instances: x 1 : (Age=29, Status=Married, Refund=No) x 2 : (Age=28, Status=Single, Refund=Yes) x 3 : (Age=38, Status=Divorced, Refund=No) • Only x 1 is covered by the rule r
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Rule Based Classifiers • Rules may not be mutually exclusive – More than one rule may cover the same instance • Strategies: – Strict enforcement of mutual exclusiveness • Avoid generating rules that have overlapping coverage with previously selected rules – Ordered rules • Rules are rank ordered according to their priority – Voting • Allow an instance to trigger multiple rules, and consider the consequent of each triggered rule as a vote for that particular class
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University of Florida CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Rule Based Classifiers • Rules may not be exhaustive • Strategy: – A default rule r d : ( ) ˠ y d can be added – The default rule has an empty antecedent and is applicable when all other rules have failed y d is known as default class and is often assigned to the majority class
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CISE department Gator Engineering Data Mining Sanjay Ranka Spring 2011 Example of Rule Based Classifier r 1 : (Refund=No) & (Marital Status=Single) & (Taxable Income>80K) ˠ Yes r 2
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This note was uploaded on 11/13/2011 for the course CIS 4930 taught by Professor Staff during the Spring '08 term at University of Florida.

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dm3part2 - University of Florida CISE department...

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