Data Mining: Introduction Lecture Notes for Chapter Introduction to Data Mining by Tan, Steinbach, Kumar © Tan,Steinbach, Kumar Introduction to Data Mining Why Mine Data? Commercial Viewpoint Lots of data is being collected and warehoused – Web data, e-commerce – purchases at department/ grocery stores – Bank/Credit Card transactions Computers have become cheaper and more powerful Competitive Pressure is Strong – Provide better, customized services for an edge (e.g in Customer Relationship Management) © Tan,Steinbach, Kumar Introduction to Data Mining Why Mine Data? Scientific Viewpoint Data collected and stored at enormous speeds (GB/hour) – remote sensors on a satellite – telescopes scanning the skies – microarrays generating gene expression data – scientific simulations generating terabytes of data Traditional techniques infeasible for raw data Data mining may help scientists – in classifying and segmenting data – in Hypothesis Formation Examples of massive data set MEDLINE text database – Records for 19 million published articles Web search engines – Multiple billion Web pages indexed – 100’s of millions of site visitors per day CALTRANS loop sensor data – GB per day NASA MODIS satellite – Coverage at 250m resolution, 37 bands, whole earth, every day Retail transaction data – Ebay, Amazon, Walmart: >100 million transactions per day – Visa, Mastercard: similar or larger numbers © Tan,Steinbach, Kumar Introduction to Data Mining Mining Large Data Sets - Motivation There is often information “hidden” in the data that is not readily evident Human analysts may take weeks to discover useful information Much of the data is never analyzed at all 4,000,000 3,500,000 The Data Gap 3,000,000 2,500,000 2,000,000 1,500,000 Total new disk (TB) since 1995 1,000,000 Number of analysts 500,000 1995 1996 1997 1998 1999 ©From: Tan,Steinbach, R Grossman, Kumar C Kamath, V Kumar, “Data Mining Introduction for Scientific to Data and Mining Engineering Applications” What is Data Mining? Many Definitions – Non-trivial extraction of implicit, previously unknown and potentially useful information from data – Exploration & analysis, by automatic or semi-automatic means, of large quantities of data in order to discover meaningful patterns © Tan,Steinbach, Kumar Introduction to Data Mining What is (not) Data Mining? What is not Data Mining? What is Data Mining? – Look up phone number in phone directory – Certain names are more prevalent in certain US locations (O’Brien, O’Rurke, O’Reilly… in Boston area) – Query a Web search engine for information about “Amazon” – Group together similar documents returned by search engine according to their context (e.g Amazon rainforest, Amazon.com,) © Tan,Steinbach, Kumar Introduction to Data Mining What is (not) Data Mining? What is not Data Mining? – Generating a histogram of salaries for different age groups – Issuing SQL query to a database, and reading the reply © Tan,Steinbach, Kumar What is Data Mining? – Finding groups of people with similar hobbies – Are chances of getting cancer higher if you live near a power line? Introduction to Data Mining Data Mining and Knowledge Discovery © Tan,Steinbach, Kumar Introduction to Data Mining Data Mining vs Statistics Traditional statistics – First hypothesize, then collect data, then analyze – Often model-oriented (strong parametric models) Data mining – Few if any a priori hypotheses – Data is usually already collect a priori – Analysis is typically data-driven not hypothesis-driven – Often algorithm-oriented rather than model-oriented Different? – Yes, in terms of culture, motivation – Statistical ideas are very useful in data mining – Increasing overlap at the boundary of statistics and data mining © Tan,Steinbach, Kumar Introduction to Data Mining 10 Regression Linear regression – Data is modeled using a straight line – Y = a + bX © Tan,Steinbach, Kumar Introduction to Data Mining 28 Regression Non-linear regression – Data is modeled using a nonlinear function – Y = a + b * f(X) © Tan,Steinbach, Kumar Introduction to Data Mining 29 Clustering Definition Given a set of data points, each having a set of attributes, and a similarity measure among them, find clusters such that – Data points in one cluster are more similar to one another – Data points in separate clusters are less similar to one another Similarity Measures: – Euclidean Distance if attributes are continuous – Other Problem-specific Measures © Tan,Steinbach, Kumar Introduction to Data Mining 30 © Tan,Steinbach, Kumar Introduction to Data Mining 31 Clustering: Application Market Segmentation: – Goal: subdivide a market into distinct subsets of customers where any subset may conceivably be selected as a market target to be reached with a distinct marketing mix – Approach: Collect different attributes of customers based on their geographical and lifestyle related information Find clusters of similar customers Measure the clustering quality by observing buying patterns of customers in same cluster vs those from different clusters © Tan,Steinbach, Kumar Introduction to Data Mining 32 Clustering: Application Document Clustering: – Goal: To find groups of documents that are similar to each other based on the important terms appearing in them – Approach: To identify frequently occurring terms in each document Form a similarity measure based on the frequencies of different terms Use it to cluster – Gain: Information Retrieval can utilize the clusters to relate a new document or search term to clustered documents © Tan,Steinbach, Kumar Introduction to Data Mining 33 Illustrating Document Clustering Clustering Points: 3204 Articles of Los Angeles Times Similarity Measure: How many words are common in these documents (after some word filtering) Category Total Articles Correctly Placed 555 364 Foreign 341 260 National 273 36 Metro 943 746 Sports 738 573 Entertainment 354 278 Financial © Tan,Steinbach, Kumar Introduction to Data Mining 34 Clustering of S&P 500 Stock Data Observe Stock Movements every day Clustering points: Stock-{UP/DOWN} Similarity Measure: Two points are more similar if the events described by them frequently happen together on the same day We used association rules to quantify a similarity measure Discovered Clusters Applied-Matl-DOW N,Bay-Net work-Down,3-COM-DOWN, Cabletron-Sys-DOWN,CISCO-DOWN,HP-DOWN, DSC-Co mm-DOW N,INTEL-DOWN,LSI-Logic-DOWN, Micron-Tech-DOWN,Texas-Inst-Down,Tellabs-Inc-Down, Natl-Semiconduct-DOWN,Oracl-DOWN,SGI-DOW N, Sun-DOW N Apple-Co mp-DOW N,Autodesk-DOWN,DEC-DOWN, ADV-M icro-Device-DOWN,Andrew-Corp-DOWN, Co mputer-Assoc-DOWN,Circuit-City-DOWN, Co mpaq-DOWN, EM C-Corp-DOWN, Gen-Inst-DOWN, Motorola-DOW N,Microsoft-DOWN,Scientific-Atl-DOWN © Tan,Steinbach, Kumar Industry Group Technology1-DOWN Technology2-DOWN Fannie-Mae-DOWN,Fed-Ho me-Loan-DOW N, MBNA-Corp -DOWN,Morgan-Stanley-DOWN Baker-Hughes-UP,Dresser-Inds-UP,Halliburton-HLD-UP, Louisiana-Land-UP,Phillips-Petro-UP,Unocal-UP, Schlu mberger-UP Introduction to Data Mining Financial-DOWN Oil-UP 35 Association Rule Discovery: Definition Given a set of records each of which contain some number of items from a given collection; – Produce dependency rules which will predict occurrence of an item based on occurrences of other items TID Items Bread, Coke, Milk Beer, Bread Beer, Coke, Diaper, Milk Beer, Bread, Diaper, Milk Coke, Diaper, Milk © Tan,Steinbach, Kumar Rules Discovered: {Milk} > {Coke} {Diaper, Milk} > {Beer} Introduction to Data Mining 36 Association Rule Discovery: Application Marketing and Sales Promotion: – Let the rule discovered be {Bagels, … } > {Potato Chips} – Potato Chips as consequent => Can be used to determine what should be done to boost its sales – Bagels in the antecedent => Can be used to see which products would be affected if the store discontinues selling bagels – Bagels in antecedent and Potato chips in consequent => Can be used to see what products should be sold with Bagels to promote sale of Potato chips! © Tan,Steinbach, Kumar Introduction to Data Mining 37 Association Rule Discovery: Application Supermarket shelf management – Goal: To identify items that are bought together by sufficiently many customers – Approach: Process the point-of-sale data collected with barcode scanners to find dependencies among items – A classic rule - If a customer buys diaper and milk, then he is very likely to buy beer So, don’t be surprised if you find six-packs stacked next to diapers! © Tan,Steinbach, Kumar Introduction to Data Mining 38 Deviation/Anomaly Detection Detect significant deviations from normal behavior Applications: – Credit Card Fraud Detection – Network Intrusion Detection Typical network traffic at University level may reach over 100 million connections per day © Tan,Steinbach, Kumar Introduction to Data Mining 39 Credit card fraud detection Goal: to detect fraudulent credit card transactions Approach: – Based on past usage patterns, develop model for authorized credit card transactions – Check for deviation form model, before authenticating new credit card transactions – Hold payment and verify authenticity of “doubtful” transactions by other means (phone call, …) © Tan,Steinbach, Kumar Introduction to Data Mining 40 Network intrusion detection Goal: to detect intrusion of a computer Approach – Define and develop a model for normal user behavior on the computer network – Continuously monitor behavior of users to check if it deviates from the defined normal behavior – Raise an alarm, if such deviation is found © Tan,Steinbach, Kumar Introduction to Data Mining 41 Challenges of Data Mining Scalability Dimensionality Complex and Heterogeneous Data Data Quality Data Ownership and Distribution Privacy Preservation Streaming Data © Tan,Steinbach, Kumar Introduction to Data Mining 42