Data Mining Introduction What is data mining The

Data Mining Introduction

What is data mining The discovery of new information in terms of patterns or rules from vast amounts of data Process of semi-automatically analyzing large databases to find patterns that are: ◦ valid: hold on new data with some certainity ◦ novel: non-obvious to the system ◦ useful: should be possible to act on the item ◦ understandable: humans should be able to interpret the pattern

knowledge discovery in databases (KDD) Data mining is actually one step of a larger process known as knowledge discovery in databases (KDD). The KDD process model comprises six phases: ◦ ◦ ◦ Data selection Data cleansing Enrichment Data transformation or encoding Data mining Reporting and displaying discovered knowledge

Why Data Mining? 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

Why Data Mining? Banking: loan/credit card approval Customer relationship management: Targeted marketing: ◦ predict good customers based on old customers ◦ identify those who are likely to leave for a competitor. ◦ identify likely responders to promotions Fraud detection: telecommunications, financial transactions ◦ from an online stream of event identify fraudulent events Manufacturing and production: ◦ automatically adjust knobs when process parameter changes

Why Data Mining? Medicine: disease outcome, effectiveness of treatments ◦ analyze patient disease history: find relationship between diseases Molecular/Pharmaceutical: identify new drugs Scientific data analysis: ◦ identify new galaxies by searching for sub clusters Web site/store design and promotion: ◦ find affinity of visitor to pages and modify layout

Origins of Data Mining Draws ideas from machine learning/AI, pattern recognition, statistics, and database systems Traditional Techniques Machine Learning/ Statistics/ Pattern AI may be unsuitable due to ◦ Enormity of data ◦ High dimensionality of data ◦ Heterogeneous, distributed nature of data Recognition Data Mining Database systems

Data Mining Tasks Prediction Methods ◦ Use some variables to predict unknown or future values of other variables. Description Methods ◦ Find human-interpretable patterns that describe the data.

Some basic operations Predictive: ◦ Regression ◦ Classification ◦ Deviation Detection Descriptive: ◦ Clustering / similarity matching ◦ Association rules and variants ◦ Sequential Pattern

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

What is (not) Data Mining? l What is not Data Mining? – Look up phone number in phone directory – Query a Web search engine for information about “Amazon” l What is Data Mining? – Certain names are more prevalent in certain US locations (O’Brien, O’Rurke, O’Reilly… in Boston area) – Group together similar documents returned by search engine according to their context (e. g. Amazon rainforest, Amazon. com, )

Classification

Classification Given old data about customers and payments, predict new applicant’s loan eligibility. Previous customers Classifier Decision rules Salary > 5 L Age Salary Profession Location Customer type Prof. = Exec New applicant’s data Good/ bad

Classification: Definition Given a collection of records (training set ) ◦ Each record contains a set of attributes, one of the attributes is the class. Find a model for class attribute as a function of the values of other attributes. Goal: previously unseen records should be assigned a class as accurately as possible. ◦ A test set is used to determine the accuracy of the model. Usually, the given data set is divided into training and test sets, with training set used to build the model and test set used to validate it.

Classification methods Regression: (linear or any other polynomial) ◦ a*x 1 + b*x 2 + c = Ci. Nearest neighour Decision tree classifier: divide decision space into piecewise constant regions. Probabilistic/generative models Neural networks: partition by non-linear boundaries

Classification Example a ric l l ir ca o o c g ate nt o c in us o u s s cla Test Set Training Set Learn Classifier Model

Classification: Application 1 Direct Marketing ◦ Goal: Reduce cost of mailing by targeting a set of consumers likely to buy a new cell-phone product. ◦ Approach: Use the data for a similar product introduced before. We know which customers decided to buy and which decided otherwise. This {buy, don’t buy} decision forms the class attribute. Collect various demographic, lifestyle, and companyinteraction related information about all such customers. Type of business, where they stay, how much they earn, etc. Use this information as input attributes to learn a classifier model.

Classification: Application 2 Fraud Detection ◦ Goal: Predict fraudulent cases in credit card transactions. ◦ Approach: Use credit card transactions and the information on its account-holder as attributes. When does a customer buy, what does he buy, how often he pays on time, etc Label past transactions as fraud or fair transactions. This forms the class attribute. Learn a model for the class of the transactions. Use this model to detect fraud by observing credit card transactions on an account.

Classification: Application 3 Sky Survey Cataloging ◦ Goal: To predict class (star or galaxy) of sky objects, especially visually faint ones, based on the telescopic survey images (from Palomar Observatory). 3000 images with 23, 040 x 23, 040 pixels per image. ◦ Approach: Segment the image. Measure image attributes (features) - 40 of them per object. Model the class based on these features. Success Story: Could find 16 new high red-shift quasars, some of the farthest objects that are difficult to find!

Classifying Galaxies Early Class: • Stages of Formation Courtesy: http: //aps. umn. edu Attributes: • Image features, • Characteristics of light waves received, etc. Intermediate Late Data Size: • 72 million stars, 20 million galaxies • Object Catalog: 9 GB • Image Database: 150 GB

Clustering

Clustering Unsupervised learning when old data with class labels not available e. g. when introducing a new product. Group/cluster existing customers based on time series of payment history such that similar customers in same cluster. Key requirement: Need a good measure of similarity between instances. Identify micro-markets and develop policies for each

Illustrating Clustering x. Euclidean Distance Based Clustering in 3 -D space. Intracluster distances are minimized Intercluster distances are maximized

Applications Customer segmentation e. g. for targeted marketing ◦ Group/cluster existing customers based on time series of payment history such that similar customers in same cluster. ◦ Identify micro-markets and develop policies for each Collaborative filtering: ◦ group based on common items purchased Text clustering Compression

Clustering methods Hierarchical clustering ◦ agglomerative Vs divisive ◦ single link Vs complete link Partitional clustering ◦ distance-based: K-means ◦ model-based: EM ◦ density-based

Clustering: Application 1 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.

Clustering: Application 2 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.

Illustrating Document Clustering Points: 3204 Articles of Los Angeles Times. Similarity Measure: How many words are common in these documents (after some word filtering).

Association Rules

Association rules T Given set T of groups of items Example: set of item sets purchased Goal: find all rules on itemsets of the form a-->b such that ◦ support of a and b > user threshold s ◦ conditional probability (confidence) of b given a > user threshold c Example: Milk --> bread Purchase of product A --> service B Milk, cereal Tea, milk Tea, rice, bread cereal

Variants High confidence may not imply high correlation Use correlations. Find expected support and large departures from that interesting. . ◦ see statistical literature on contingency tables. Still too many rules, need to prune. . .

Prevalent Interesting Analysts already know about prevalent rules Interesting rules are those that deviate from prior expectation Mining’s payoff is in finding surprising phenomena 1995 1998 Zzzz. . . Milk and cereal sell together!

What makes a rule surprising? Does not match prior expectation ◦ Correlation between milk and cereal remains roughly constant over time Cannot be trivially derived from simpler rules ◦ Milk 10%, cereal 10% ◦ Milk and cereal 10% … surprising ◦ Eggs 10% ◦ Milk, cereal and eggs 0. 1% … surprising! ◦ Expected 1%

Applications of fast itemset counting Find correlated events: Applications in medicine: find redundant tests Cross selling in retail, banking Improve predictive capability of classifiers that assume attribute independence New similarity measures of categorical attributes [Mannila et al, KDD 98]

Association Rule Discovery: Application 1 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!

Association Rule Discovery: Application 2 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.

Sequential Pattern Discovery

Sequential Pattern Discovery: Definition Given is a set of objects, with each object associated with its own timeline of events, find rules that predict strong sequential dependencies among different events. (A B) (C) (D E) Rules are formed by first disovering patterns. Event occurrences in the patterns are governed by timing constraints. (A B) <= xg (C) (D E) >ng <= ws <= ms

Sequential Pattern Discovery: Examples In telecommunications alarm logs, ◦ (Inverter_Problem Excessive_Line_Current) (Rectifier_Alarm) --> (Fire_Alarm) In point-of-sale transaction sequences, ◦ Computer Bookstore: (Intro_To_Visual_C) (C++_Primer) --> (Perl_for_dummies, Tcl_Tk) ◦ Athletic Apparel Store: (Shoes) (Racket, Racketball) --> (Sports_Jacket)

Regression

Regression Predict a value of a given continuous valued variable based on the values of other variables, assuming a linear or nonlinear model of dependency. Greatly studied in statistics, neural network fields. Examples: ◦ Predicting sales amounts of new product based on advetising expenditure. ◦ Predicting wind velocities as a function of temperature, humidity, air pressure, etc.

Deviation/Anomaly Detection

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

Challenges of Data Mining Scalability Dimensionality Complex and Heterogeneous Data Quality Data Ownership and Distribution Privacy Preservation Streaming Data

Data Mining in Practice

Application Areas Industry Finance Insurance Telecommunication Transport Consumer goods Data Service providers Utilities Application Credit Card Analysis Claims, Fraud Analysis Call record analysis Logistics management promotion analysis Value added data Power usage analysis

Why Now? Data is being produced Data is being warehoused The computing power is available The computing power is affordable The competitive pressures are strong Commercial products are available

Data Mining works with Warehouse Data Warehousing provides the Enterprise with a memory Data Mining provides the Enterprise with intelligence

Usage scenarios Data warehouse mining: ◦ assimilate data from operational sources ◦ mine static data Mining log data Continuous mining: example in process control Stages in mining: ◦ data selection pre-processing: cleaning transformation mining result evaluation visualization

Mining market Around 20 to 30 mining tool vendors Major tool players: ◦ ◦ Clementine, IBM’s Intelligent Miner, SGI’s Mine. Set, SAS’s Enterprise Miner. ◦ ◦ fraud detection: electronic commerce applications, health care, customer relationship management: Epiphany All pretty much the same set of tools Many embedded products:

Vertical integration: Mining on the web Web log analysis for site design: ◦ what are popular pages, ◦ what links are hard to find. Electronic stores sales enhancements: ◦ recommendations, advertisement: ◦ Collaborative filtering: Net perception, Wisewire ◦ Inventory control: what was a shopper looking for and could not find. .

OLAP Mining integration OLAP (On Line Analytical Processing) ◦ Fast interactive exploration of multidim. aggregates. ◦ Heavy reliance on manual operations for analysis: ◦ Tedious and error-prone on large multidimensional data Ideal platform for vertical integration of mining but needs to be interactive instead of batch.

Data Mining in Use The US Government uses Data Mining to track fraud A Supermarket becomes an information broker Basketball teams use it to track game strategy Cross Selling Target Marketing Holding on to Good Customers Weeding out Bad Customers