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  1. 1. Friday, 12 January 2007 William H. Hsu Department of Computing and Information Sciences, KSU http:// www.kddresearch.org http:// www.cis.ksu.edu/~bhsu Readings: Chapter 1, Mitchell A Brief Survey of Machine Learning CIS 732/830: Lecture 0
  2. 2. Lecture Outline <ul><li>Course Information: Format, Exams, Homework, Programming, Grading </li></ul><ul><li>Class Resources: Course Notes, Web/News/Mail, Reserve Texts </li></ul><ul><li>Overview </li></ul><ul><ul><li>Topics covered </li></ul></ul><ul><ul><li>Applications </li></ul></ul><ul><ul><li>Why machine learning? </li></ul></ul><ul><li>Brief Tour of Machine Learning </li></ul><ul><ul><li>A case study </li></ul></ul><ul><ul><li>A taxonomy of learning </li></ul></ul><ul><ul><li>Intelligent systems engineering: specification of learning problems </li></ul></ul><ul><li>Issues in Machine Learning </li></ul><ul><ul><li>Design choices </li></ul></ul><ul><ul><li>The performance element: intelligent systems </li></ul></ul><ul><li>Some Applications of Learning </li></ul><ul><ul><li>Database mining, reasoning (inference/decision support), acting </li></ul></ul><ul><ul><li>Industrial usage of intelligent systems </li></ul></ul>
  3. 3. Course Information and Administrivia <ul><li>Instructor: William H. Hsu </li></ul><ul><ul><li>E-mail: [email_address] </li></ul></ul><ul><ul><li>Office phone: (785) 532-6350 x29; home phone: (785) 539-7180; ICQ 28651394 </li></ul></ul><ul><ul><li>Office hours: Wed/Thu/Fri (213 Nichols); by appointment, Tue </li></ul></ul><ul><li>Grading </li></ul><ul><ul><li>Assignments (8): 32%, paper reviews (13): 10%, midterm: 20%, final: 25% </li></ul></ul><ul><ul><li>Class participation: 5% </li></ul></ul><ul><ul><li>Lowest homework score and lowest 3 paper summary scores dropped </li></ul></ul><ul><li>Homework </li></ul><ul><ul><li>Eight assignments: written (5) and programming (3) – drop lowest </li></ul></ul><ul><ul><li>Late policy: due on Fridays </li></ul></ul><ul><ul><li>Cheating: don’t do it; see class web page for policy </li></ul></ul><ul><li>Project Option </li></ul><ul><ul><li>CIS 690/890 project option for graduate students </li></ul></ul><ul><ul><li>Term paper or semester research project; sign up by 09 Feb 2007 </li></ul></ul>
  4. 4. Class Resources <ul><li>Web Page (Required) </li></ul><ul><ul><li>http://www.kddresearch.org/Courses/Spring-2007/CIS732 </li></ul></ul><ul><ul><li>Lecture notes (MS PowerPoint XP, PDF) </li></ul></ul><ul><ul><li>Homeworks (MS PowerPoint XP, PDF) </li></ul></ul><ul><ul><li>Exam and homework solutions (MS PowerPoint XP, PDF) </li></ul></ul><ul><ul><li>Class announcements (students responsibility to follow) and grade postings </li></ul></ul><ul><li>Course Notes at Copy Center (Required) </li></ul><ul><li>Course Web Group </li></ul><ul><ul><li>Mirror of announcements from class web page </li></ul></ul><ul><ul><li>Discussions (instructor and other students) </li></ul></ul><ul><ul><li>Dated research announcements (seminars, conferences, calls for papers) </li></ul></ul><ul><li>Mailing List (Automatic) </li></ul><ul><ul><li>[email_address] </li></ul></ul><ul><ul><li>Sign-up sheet </li></ul></ul><ul><ul><li>Reminders, related research announcements </li></ul></ul>
  5. 5. Course Overview <ul><li>Learning Algorithms and Models </li></ul><ul><ul><li>Models: decision trees, linear threshold units (winnow, weighted majority), neural networks, Bayesian networks (polytrees, belief networks, influence diagrams, HMMs), genetic algorithms, instance-based (nearest-neighbor) </li></ul></ul><ul><ul><li>Algorithms (e.g., for decision trees): ID3, C4.5, CART, OC1 </li></ul></ul><ul><ul><li>Methodologies: supervised, unsupervised, reinforcement; knowledge-guided </li></ul></ul><ul><li>Theory of Learning </li></ul><ul><ul><li>Computational learning theory (COLT): complexity, limitations of learning </li></ul></ul><ul><ul><li>Probably Approximately Correct (PAC) learning </li></ul></ul><ul><ul><li>Probabilistic, statistical, information theoretic results </li></ul></ul><ul><li>Multistrategy Learning: Combining Techniques, Knowledge Sources </li></ul><ul><li>Data: Time Series, Very Large Databases (VLDB), Text Corpora </li></ul><ul><li>Applications </li></ul><ul><ul><li>Performance element: classification, decision support, planning, control </li></ul></ul><ul><ul><li>Database mining and knowledge discovery in databases (KDD) </li></ul></ul><ul><ul><li>Computer inference: learning to reason </li></ul></ul>
  6. 6. Why Machine Learning? <ul><li>New Computational Capability </li></ul><ul><ul><li>Database mining: converting (technical) records into knowledge </li></ul></ul><ul><ul><li>Self-customizing programs: learning news filters, adaptive monitors </li></ul></ul><ul><ul><li>Learning to act: robot planning, control optimization, decision support </li></ul></ul><ul><ul><li>Applications that are hard to program: automated driving, speech recognition </li></ul></ul><ul><li>Better Understanding of Human Learning and Teaching </li></ul><ul><ul><li>Cognitive science: theories of knowledge acquisition (e.g., through practice) </li></ul></ul><ul><ul><li>Performance elements: reasoning (inference) and recommender systems </li></ul></ul><ul><li>Time is Right </li></ul><ul><ul><li>Recent progress in algorithms and theory </li></ul></ul><ul><ul><li>Rapidly growing volume of online data from various sources </li></ul></ul><ul><ul><li>Available computational power </li></ul></ul><ul><ul><li>Growth and interest of learning-based industries (e.g., data mining/KDD) </li></ul></ul>
  7. 7. Rule and Decision Tree Learning <ul><li>Example: Rule Acquisition from Historical Data </li></ul><ul><li>Data </li></ul><ul><ul><li>Patient 103 (time = 1): Age 23, First-Pregnancy: no, Anemia: no, Diabetes: no, Previous-Premature-Birth: no, Ultrasound: unknown , Elective C-Section: unknown , Emergency-C-Section: unknown </li></ul></ul><ul><ul><li>Patient 103 (time = 2): Age 23, First-Pregnancy: no, Anemia: no, Diabetes: yes , Previous-Premature-Birth: no, Ultrasound: abnormal , Elective C-Section: no, Emergency-C-Section: unknown </li></ul></ul><ul><ul><li>Patient 103 (time = n): Age 23, First-Pregnancy: no, Anemia: no, Diabetes: no, Previous-Premature-Birth: no, Ultrasound: unknown , Elective C-Section: no, Emergency-C-Section: YES </li></ul></ul><ul><li>Learned Rule </li></ul><ul><ul><li>IF no previous vaginal delivery , AND abnormal 2nd trimester ultrasound , AND malpresentation at admission , AND no elective C-Section THEN probability of emergency C-Section is 0.6 </li></ul></ul><ul><ul><li>Training set: 26/41 = 0.634 </li></ul></ul><ul><ul><li>Test set: 12/20 = 0.600 </li></ul></ul>
  8. 8. Neural Network Learning <ul><li>A utonomous L earning V ehicle I n a N eural N et (ALVINN): Pomerleau et al </li></ul><ul><ul><li>http://www.ri.cmu.edu/projects/project_160.html </li></ul></ul><ul><ul><li>Drives 70mph on highways </li></ul></ul>
  9. 9. Relevant Disciplines <ul><li>Artificial Intelligence </li></ul><ul><li>Bayesian Methods </li></ul><ul><li>Cognitive Science </li></ul><ul><li>Computational Complexity Theory </li></ul><ul><li>Control Theory </li></ul><ul><li>Information Theory </li></ul><ul><li>Neuroscience </li></ul><ul><li>Philosophy </li></ul><ul><li>Psychology </li></ul><ul><li>Statistics </li></ul>Machine Learning Symbolic Representation Planning/Problem Solving Knowledge-Guided Learning Bayes’s Theorem Missing Data Estimators PAC Formalism Mistake Bounds Language Learning Learning to Reason Optimization Learning Predictors Meta-Learning Entropy Measures MDL Approaches Optimal Codes ANN Models Modular Learning Occam’s Razor Inductive Generalization Power Law of Practice Heuristic Learning Bias/Variance Formalism Confidence Intervals Hypothesis Testing
  10. 10. Specifying A Learning Problem <ul><li>Learning = Improving with Experience at Some Task </li></ul><ul><ul><li>Improve over task T, </li></ul></ul><ul><ul><li>with respect to performance measure P , </li></ul></ul><ul><ul><li>based on experience E . </li></ul></ul><ul><li>Example: Learning to Play Checkers </li></ul><ul><ul><li>T : play games of checkers </li></ul></ul><ul><ul><li>P : percent of games won in world tournament </li></ul></ul><ul><ul><li>E : opportunity to play against self </li></ul></ul><ul><li>Refining the Problem Specification: Issues </li></ul><ul><ul><li>What experience? </li></ul></ul><ul><ul><li>What exactly should be learned? </li></ul></ul><ul><ul><li>How shall it be represented ? </li></ul></ul><ul><ul><li>What specific algorithm to learn it? </li></ul></ul><ul><li>Defining the Problem Milieu </li></ul><ul><ul><li>Performance element: How shall the results of learning be applied? </li></ul></ul><ul><ul><li>How shall the performance element be evaluated? The learning system? </li></ul></ul>
  11. 11. Example: Learning to Play Checkers <ul><li>Type of Training Experience </li></ul><ul><ul><li>Direct or indirect? </li></ul></ul><ul><ul><li>Teacher or not? </li></ul></ul><ul><ul><li>Knowledge about the game (e.g., openings/endgames)? </li></ul></ul><ul><li>Problem: Is Training Experience Representative (of Performance Goal)? </li></ul><ul><li>Software Design </li></ul><ul><ul><li>Assumptions of the learning system: legal move generator exists </li></ul></ul><ul><ul><li>Software requirements: generator, evaluator(s), parametric target function </li></ul></ul><ul><li>Choosing a Target Function </li></ul><ul><ul><li>ChooseMove: Board  Move (action selection function, or policy ) </li></ul></ul><ul><ul><li>V: Board  R (board evaluation function) </li></ul></ul><ul><ul><li>Ideal target V ; approximated target </li></ul></ul><ul><ul><li>Goal of learning process: operational description (approximation) of V </li></ul></ul>
  12. 12. A Target Function for Learning to Play Checkers <ul><li>Possible Definition </li></ul><ul><ul><li>If b is a final board state that is won, then V(b) = 100 </li></ul></ul><ul><ul><li>If b is a final board state that is lost, then V(b) = -100 </li></ul></ul><ul><ul><li>If b is a final board state that is drawn, then V(b) = 0 </li></ul></ul><ul><ul><li>If b is not a final board state in the game, then V(b) = V(b’) where b’ is the best final board state that can be achieved starting from b and playing optimally until the end of the game </li></ul></ul><ul><ul><li>Correct values, but not operational </li></ul></ul><ul><li>Choosing a Representation for the Target Function </li></ul><ul><ul><li>Collection of rules? </li></ul></ul><ul><ul><li>Neural network? </li></ul></ul><ul><ul><li>Polynomial function (e.g., linear, quadratic combination) of board features? </li></ul></ul><ul><ul><li>Other? </li></ul></ul><ul><li>A Representation for Learned Function </li></ul><ul><ul><li>bp/rp = number of black/red pieces; bk/rk = number of black/red kings; bt/rt = number of black/red pieces threatened (can be taken on next turn) </li></ul></ul>
  13. 13. A Training Procedure for Learning to Play Checkers <ul><li>Obtaining Training Examples </li></ul><ul><ul><li>the target function </li></ul></ul><ul><ul><li>the learned function </li></ul></ul><ul><ul><li>the training value </li></ul></ul><ul><li>One Rule For Estimating Training Values: </li></ul><ul><li>Choose Weight Tuning Rule </li></ul><ul><ul><li>Least Mean Square (LMS) weight update rule: REPEAT </li></ul></ul><ul><ul><ul><ul><li>Select a training example b at random </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Compute the error(b) for this training example </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For each board feature f i , update weight w i as follows: where c is a small, constant factor to adjust the learning rate </li></ul></ul></ul></ul>
  14. 14. Design Choices for Learning to Play Checkers Completed Design Determine Type of Training Experience Games against experts Games against self Table of correct moves Determine Target Function Board  value Board  move Determine Representation of Learned Function Polynomial Linear function of six features Artificial neural network Determine Learning Algorithm Gradient descent Linear programming
  15. 15. Some Issues in Machine Learning <ul><li>What Algorithms Can Approximate Functions Well? When? </li></ul><ul><li>How Do Learning System Design Factors Influence Accuracy? </li></ul><ul><ul><li>Number of training examples </li></ul></ul><ul><ul><li>Complexity of hypothesis representation </li></ul></ul><ul><li>How Do Learning Problem Characteristics Influence Accuracy? </li></ul><ul><ul><li>Noisy data </li></ul></ul><ul><ul><li>Multiple data sources </li></ul></ul><ul><li>What Are The Theoretical Limits of Learnability? </li></ul><ul><li>How Can Prior Knowledge of Learner Help? </li></ul><ul><li>What Clues Can We Get From Biological Learning Systems? </li></ul><ul><li>How Can Systems Alter Their Own Representation? </li></ul>
  16. 16. Interesting Applications Reasoning (Inference, Decision Support) Cartia ThemeScapes - http:// www.cartia.com 6500 news stories from the WWW in 1997 Planning, Control Normal Ignited Engulfed Destroyed Extinguished Fire Alarm Flooding DC-ARM - http://www- kbs.ai.uiuc.edu Database Mining NCSA D2K - http:// alg.ncsa.uiuc.edu
  17. 17. Lecture Outline <ul><li>Read: Chapter 2, Mitchell; Section 5.1.2, Buchanan and Wilkins </li></ul><ul><li>Suggested Exercises: 2.2, 2.3, 2.4, 2.6 </li></ul><ul><li>Taxonomy of Learning Systems </li></ul><ul><li>Learning from Examples </li></ul><ul><ul><li>(Supervised) concept learning framework </li></ul></ul><ul><ul><li>Simple approach: assumes no noise; illustrates key concepts </li></ul></ul><ul><li>General-to-Specific Ordering over Hypotheses </li></ul><ul><ul><li>Version space: partially-ordered set (poset) formalism </li></ul></ul><ul><ul><li>Candidate elimination algorithm </li></ul></ul><ul><ul><li>Inductive learning </li></ul></ul><ul><li>Choosing New Examples </li></ul><ul><li>Next Week </li></ul><ul><ul><li>The need for inductive bias: 2.7, Mitchell; 2.4.1-2.4.3, Shavlik and Dietterich </li></ul></ul><ul><ul><li>Computational learning theory (COLT): Chapter 7, Mitchell </li></ul></ul><ul><ul><li>PAC learning formalism: 7.2-7.4, Mitchell; 2.4.2, Shavlik and Dietterich </li></ul></ul>
  18. 18. What to Learn? <ul><li>Classification Functions </li></ul><ul><ul><li>Learning hidden functions: estimating (“fitting”) parameters </li></ul></ul><ul><ul><li>Concept learning (e.g., chair, face, game) </li></ul></ul><ul><ul><li>Diagnosis, prognosis: medical, risk assessment, fraud, mechanical systems </li></ul></ul><ul><li>Models </li></ul><ul><ul><li>Map (for navigation) </li></ul></ul><ul><ul><li>Distribution (query answering, aka QA) </li></ul></ul><ul><ul><li>Language model (e.g., automaton/grammar) </li></ul></ul><ul><li>Skills </li></ul><ul><ul><li>Playing games </li></ul></ul><ul><ul><li>Planning </li></ul></ul><ul><ul><li>Reasoning (acquiring representation to use in reasoning) </li></ul></ul><ul><li>Cluster Definitions for Pattern Recognition </li></ul><ul><ul><li>Shapes of objects </li></ul></ul><ul><ul><li>Functional or taxonomic definition </li></ul></ul><ul><li>Many Problems Can Be Reduced to Classification </li></ul>
  19. 19. How to Learn It? <ul><li>Supervised </li></ul><ul><ul><li>What is learned? Classification function; other models </li></ul></ul><ul><ul><li>Inputs and outputs? Learning: </li></ul></ul><ul><ul><li>How is it learned? Presentation of examples to learner (by teacher) </li></ul></ul><ul><li>Unsupervised </li></ul><ul><ul><li>Cluster definition, or vector quantization function ( codebook ) </li></ul></ul><ul><ul><li>Learning: </li></ul></ul><ul><ul><li>Formation, segmentation, labeling of clusters based on observations, metric </li></ul></ul><ul><li>Reinforcement </li></ul><ul><ul><li>Control policy (function from states of the world to actions) </li></ul></ul><ul><ul><li>Learning: </li></ul></ul><ul><ul><li>(Delayed) feedback of reward values to agent based on actions selected; model updated based on reward, (partially) observable state </li></ul></ul>
  20. 20. (Supervised) Concept Learning <ul><li>Given: Training Examples < x, f(x) > of Some Unknown Function f </li></ul><ul><li>Find: A Good Approximation to f </li></ul><ul><li>Examples (besides Concept Learning) </li></ul><ul><ul><li>Disease diagnosis </li></ul></ul><ul><ul><ul><li>x = properties of patient (medical history, symptoms, lab tests) </li></ul></ul></ul><ul><ul><ul><li>f = disease (or recommended therapy) </li></ul></ul></ul><ul><ul><li>Risk assessment </li></ul></ul><ul><ul><ul><li>x = properties of consumer, policyholder (demographics, accident history) </li></ul></ul></ul><ul><ul><ul><li>f = risk level (expected cost) </li></ul></ul></ul><ul><ul><li>Automatic steering </li></ul></ul><ul><ul><ul><li>x = bitmap picture of road surface in front of vehicle </li></ul></ul></ul><ul><ul><ul><li>f = degrees to turn the steering wheel </li></ul></ul></ul><ul><ul><li>Part-of-speech tagging </li></ul></ul><ul><ul><li>Fraud/intrusion detection </li></ul></ul><ul><ul><li>Web log analysis </li></ul></ul><ul><ul><li>Multisensor integration and prediction </li></ul></ul>
  21. 21. A Learning Problem Unknown Function x 1 x 2 x 3 x 4 y = f (x 1 , x 2 , x 3 , x 4 ) <ul><li>x i : t i , y: t, f : (t 1  t 2  t 3  t 4 )  t </li></ul><ul><li>Our learning function: Vector (t 1  t 2  t 3  t 4  t)  (t 1  t 2  t 3  t 4 )  t </li></ul>
  22. 22. Hypothesis Space: Unrestricted Case <ul><li>| A  B | = | B | | A | </li></ul><ul><li>| H 4  H | = | {0,1}  {0,1}  {0,1}  {0,1}  {0,1} | = 2 2 4 = 65536 function values </li></ul><ul><li>Complete Ignorance: Is Learning Possible? </li></ul><ul><ul><li>Need to see every possible input/output pair </li></ul></ul><ul><ul><li>After 7 examples, still have 2 9 = 512 possibilities (out of 65536) for f </li></ul></ul>
  23. 23. Training Examples for Concept EnjoySport <ul><li>Specification for Examples </li></ul><ul><ul><li>Similar to a data type definition </li></ul></ul><ul><ul><li>6 attributes: Sky, Temp, Humidity, Wind, Water, Forecast </li></ul></ul><ul><ul><li>Nominal-valued (symbolic) attributes - enumerative data type </li></ul></ul><ul><li>Binary (Boolean-Valued or H -Valued) Concept </li></ul><ul><li>Supervised Learning Problem: Describe the General Concept </li></ul>
  24. 24. Representing Hypotheses <ul><li>Many Possible Representations </li></ul><ul><li>Hypothesis h : Conjunction of Constraints on Attributes </li></ul><ul><li>Constraint Values </li></ul><ul><ul><li>Specific value (e.g., Water = Warm ) </li></ul></ul><ul><ul><li>Don’t care (e.g., “Water = ?” ) </li></ul></ul><ul><ul><li>No value allowed (e.g., “Water = Ø”) </li></ul></ul><ul><li>Example Hypothesis for EnjoySport </li></ul><ul><ul><li>Sky AirTemp Humidity Wind Water Forecast <Sunny ? ? Strong ? Same> </li></ul></ul><ul><ul><li>Is this consistent with the training examples? </li></ul></ul><ul><ul><li>What are some hypotheses that are consistent with the examples? </li></ul></ul>
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