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Hyper-Rectangle-Based Discriminative Data Generalization and Applications in Data Mining

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Hyper-Rectangle-Based Discriminative Data Generalization and Applications in Data Mining HYPER-RECTANGLE-BASED DISCRIMINATIVE DATA GENERALIZATION AND APPLICATIONS IN DATA MINING Byron Ju Gao B.Sc., Simon Fraser University, Fall 2002 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOROF PHILOSOPHY in the School of Computing Science @ Byron Ju Gao 2007 SIMON FRASER UNIVERSITY Spring 2007 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author. APPROVAL Name: Byron Ju Gao Degree: Doctor of Philosophy Title of thesis: Hyper-rectangle-based Discriminative Data Generalization and Applications in Data Mining Examining Committee: Dr. Anoop Sarkar Chair Dr. Martin Ester, Senior Supervisor Dr. Binay Bhattacharya, Supervisor Dr. Oliver Schulte, SFU Examiner Dr. Hui Xiong, External Examiner, Rutgers, the State University of New Jersey Date Approved: Deceuk bw g . 2006 .. 11 SIMON FRASER uNlm~mlibrary DECLARATION OF PARTIAL COPYRIGHT LICENCE The author, whose copyright is declared on the title page of this work, has granted to Simon Fraser University the right to lend this thesis, project or extended essay to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. The author has further granted permission to Simon Fraser University to keep or make a digital copy for use in its circulating collection (currently available to the public at the "Institutional Repository'' link of the SFU Library website <www.lib.sfu.ca> at: ~http:llir.lib.sfu.calhandlell8921112~)and, without changing the content, to translate the thesislproject or extended essays, if technically possible, to any medium or format for the purpose of preservation of the digital work. The author has further agreed that permission for multiple copying of this work for scholarly purposes may be granted by either the author or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without the author's written permission. Permission for public performance, or limited permission for private scholarly use, of any multimedia materials forming part of this work, may have been granted by the author. This information may be found on the separately catalogued multimedia material and in the signed Partial Copyright Licence. The original Partial Copyright Licence attesting to these terms, and signed by this author, may be found in the original bound copy of this work, retained in the Simon Fraser University Archive. Simon Fraser University Library Burnaby, BC, Canada Revised: Spring 2007 Abstract The ultimate goal of data mining is to extract knowledge from massive data. Knowledge is ideally represented as human-comprehensible patterns from which end-users can gain intuitions and insights. Axis-parallel hyper-rectangles provide interpretable generalizations for multi-dimensional data points with numerical attributes. In this dissertation, we study the fundamental problem of rectangle-based discriminative data generalization in the context of several useful data mining applications: cluster description, rule learning, and Nearest Rectangle classification. Clustering is one of the most important data mining tasks. However, most clustering methods output sets of points as clusters and do not generalize them into interpretable patterns. We perform a systematic study of cluster description, where we propose novel de- scription formats leading to enhanced expressive power and introduce novel description prob- lems specifying different trade-offs between interpretability and accuracy. We also present efficient heuristic algorithms for the introduced problems in the proposed formats. If-then rules are known to be the most expressive and human-comprehensible representa- tion of knowledge. Rectangles are essentially a special type of rules with all the attributional conditions specified whereas normal rules appear more compact. Decision rules can be used for both data classification and data description depending on whether the focus is on fu- ture data or existing data. For either scenario, smaller rule sets are desirable. We propose a novel rectangle-based and graph-based rule learning approach that finds rule sets with small cardinality. We also consider Nearest Rectangle learning to explore the data classification capacity of generalized rectangles. We show that by enforcing the so-called "right of inference", Near- est Rectangle learning can potentially become an interpretable hybrid inductive learning method with competitive accuracy. Keywords: discriminative generalization; hyper-rectangle; cluster description; Minimum Rule Set; Minimum Consistent Subset Cover; Nearest Rectangle learning To the Author of the author The One who does not need this to add to His glory. "Thinking is not the way leading to answers; Reasoning is not the way leading to truth." - B. G. Acknowledgments Upon completion of this dissertation, the good feeling of accomplishment rings a bell of the joy of my childhood, when I finished off a project of a skyscraper with toy bricks. Not quite comparable but close. In such a moment, I feel I am indebted a bit to each and every one in the world. We are not just neighbors! We are indeed siblings, sometimes referred to as enemies. My supervisor and mentor, Dr. Martin Ester, is a blessing to my life. I have been learning from him as a student, also as a human being. Although he tries to treat his students fairly with equal and ample patience, I have managed to consume more. I am truly grateful to those who have served in my supervisory and examining committees for their time and effort in reading my depth report, proposal, and dissertation and attending the exam and defence seminars. In particular, Dr. Binay Bhattacharya continuously gave me so many inspiring and constructive suggestions. Dr. Anoop Sarkar kindly compromised his schedule for mine. Dr. Hui Xiong was more than cooperative and responsive in making my defence take place as planned. Dr. Oliver Schulte spent hour after hour with me going through his detailed comments on my dissertation literally page by page. You can imagine how much patience and effort it must have taken him to make those comments, as his only compliment on my writing went to the carefully drawn figures. The research supporting this dissertation also greatly benefited from open discussions with the faculty and student members in the Database and Data Mining Lab of Simon Fraser University: Dr. Ke Wang, Dr. Jian Pei, Wen Jin, Rong Ge, Flavia Moser, Gabor Melli, Richard Frank, Christine Cheng, Xiang Zhang, Fei Chen, Arber Xu, Yuelong Jiang, Senqiang Zhou, Rong She, and Benjamin Fung. It is an honor to be affiliated with such a talented group. Each of these names, at some point of time, left me feeling inferior. A special group of people have become a constant source of joy, without which my PhD vii journey would have become much dryer: Dr. Tiko Kameda, Dr. Binay Bhattacharya, Zengjian Hu, Yi Sun, and Zhong Zhang. My memory has 640K but the ping-pong table will always be set there unfolded, with enough surrounding space allowing double plays. I owe so much to so many, I wish I could return the favor but keep the gratitude forever. No special thanks necessary to my mother, who always smiles others' smiles, grieves others' griefs. Mom, why do I not see you in your own world? ... Vlll Contents Approval ii Abstract iii Dedication v Quotation vi Acknowledgments vii Contents ix List of Tables xiii List of Figures xiv 1 Introduction 1 1.1 Motivation ..................................... 1 1.1.1 Cluster description ............................. 3 1.1.2 Rectangle-based rule learning ....................... 4 1 .1.3 Nearest Rectangle learning ........................ 5 1.2 Contributions of Dissertation ........................... 5 1.3 Organization of Dissertation ............................ 6 2 Rectangle-based Cluster Description 7 2.1 Overview ...................................... 7 2.2 Background ..................................... 9 2.2.1 Directly related research .......................... 10 2.2.2 Indirectly related research ......................... 12 2.3 Alphabets, Formats. and Languages ....................... 14 2.3.1 Preliminaries ................................ 14 2.3.2 Description alphabets ........................... 17 2.3.3 Description formats and languages .................... 19 2.4 Description Problems ................................ 23 2.4.1 Objective measures ............................. 23 2.4.2 MDA problem and MDL problem ..................... 24 2.5 Description Algorithms ............................... 26 2.5.1 Learn2Cover ................................ 26 2.5.2 DesTree ................................... 32 2.5.3 FindClans .................................. 34 2.6 Empirical Results .................................. 37 2.6.1 Comparisons with CART ......................... 37 2.6.2 Comparisons with BP ........................... 39 2.7 Summary ...................................... 41 3 Rectangle-based Rule Learning 43 3.1 Overview ...................................... 44 3.2 Problem Definition and Notations ........................ 48 3.2.1 Minimum Rule Set problem ........................ 48 3.2.2 Notations .................................. 51 3.3 Background ..................................... 52 3.3.1 Interpretable classifiers ..........................
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