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Data mining and knowledge discovery

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Title: Data mining and knowledge discovery


1
Lecture 14
Data mining and knowledge discovery
  • Introduction, or what is data mining?
  • Data warehouse and query tools
  • Decision trees
  • Case study Profiling people with high blood
    pressure
  • Summary

2
What is data mining?
  • Data is what we collect and store, and knowledge
    is what helps us to make informed decisions.
  • The extraction of knowledge from data is called
    data mining.
  • Data mining can also be defined as the
    exploration and analysis of large quantities of
    data in order to discover meaningful patterns and
    rules.
  • The ultimate goal of data mining is to discover
    knowledge.

3
Why data mining
  • The Explosive Growth of Data from terabytes to
    petabytes
  • Data collection and data availability
  • Automated data collection tools, database
    systems, Web, computerized society
  • Major sources of abundant data
  • Business Web, e-commerce, transactions, stocks,
  • Science Remote sensing, bioinformatics,
    scientific simulation,
  • Society and everyone news, digital cameras,
    YouTube
  • knowledge!

4
Why Not Traditional Data Analysis?
  • Tremendous amount of data
  • Algorithms must be highly scalable to handle such
    as tera-bytes of data
  • High-dimensionality of data
  • Micro-array may have tens of thousands of
    dimensions

5
  • High complexity of data
  • Data streams and sensor data
  • Time-series data, temporal data, sequence data
  • Structure data, graphs, social networks and
    multi-linked data
  • Heterogeneous databases and legacy databases
  • Spatial, spatiotemporal, multimedia, text and Web
    data
  • Software programs, scientific simulations
  • New and sophisticated applications

6
Knowledge Discovery (KDD) Process
Knowledge
  • Data miningcore of knowledge discovery process

Pattern Evaluation
Data Mining
Task-relevant Data
Selection
Data Warehouse
Data Cleaning
Data Integration
Databases
7
KDD Process Several Key Steps
  • Learning the application domain
  • relevant prior knowledge and goals of application
  • Creating a target data set data selection
  • Data cleaning and preprocessing (may take 60 of
    effort!)
  • Data reduction and transformation
  • Find useful features, dimensionality/variable
    reduction, invariant representation

8
KDD Process Several Key Steps
  • Choosing functions of data mining
  • summarization, classification, regression,
    association, clustering
  • Choosing the mining algorithm(s)
  • Data mining search for patterns of interest
  • Pattern evaluation and knowledge presentation
  • visualization, transformation, removing redundant
    patterns, etc.
  • Use of discovered knowledge

9
Data Mining Confluence of Multiple Disciplines
10
Architecture Typical Data Mining System
11
Data Mining Functionalities(1)
  • Frequent patterns, association, correlation vs.
    causality
  • Diaper ? Beer 0.5, 75 (Correlation or
    causality?)
  • Classification and prediction
  • Construct models (functions) that describe and
    distinguish classes or concepts for future
    prediction
  • E.g., classify countries based on (climate), or
    classify cars based on (gas mileage)
  • Predict some unknown or missing numerical values

12
Data Mining Functionalities(2)
  • Cluster analysis
  • Class label is unknown Group data to form new
    classes, e.g., cluster houses to find
    distribution patterns
  • Maximizing intra-class similarity minimizing
    interclass similarity
  • Outlier analysis
  • Outlier Data object that does not comply with
    the general behavior of the data
  • Noise or exception? Useful in fraud detection,
    rare events analysis

13
Data Mining Functionalities(3)
  • Trend and evolution analysis
  • Trend and deviation e.g., regression analysis
  • Sequential pattern mining e.g., digital camera ?
    large SD memory
  • Periodicity analysis
  • Similarity-based analysis
  • Other pattern-directed or statistical analyses

14
Top-10 Most Popular DM Algorithms18 Identified
Candidates (I)
  • Classification
  • 1. C4.5 Quinlan, J. R. C4.5 Programs for
    Machine Learning. Morgan Kaufmann., 1993.
  • 2. CART L. Breiman, J. Friedman, R. Olshen, and
    C. Stone. Classification and Regression Trees.
    Wadsworth, 1984.
  • 3. K Nearest Neighbours (kNN) Hastie, T. and
    Tibshirani, R. 1996. Discriminant Adaptive
    Nearest Neighbor Classification. TPAMI. 18(6)
  • 4. Naive Bayes Hand, D.J., Yu, K., 2001. Idiot's
    Bayes Not So Stupid After All? Internat.
    Statist. Rev. 69, 385-398.

15
(II)
  • Statistical Learning
  • 5. SVM Vapnik, V. N. 1995. The Nature of
    Statistical Learning Theory. Springer-Verlag.
  • 6. EM McLachlan, G. and Peel, D. (2000).
    Finite Mixture Models. J. Wiley, New York.
    Association Analysis
  • 7. Apriori Rakesh Agrawal and Ramakrishnan
    Srikant. Fast Algorithms for Mining Association
    Rules. In VLDB '94.
  • 8. FP-Tree Han, J., Pei, J., and Yin, Y. 2000.
    Mining frequent patterns without candidate
    generation. In SIGMOD '00.

16
(III)
  • Link Mining
  • 9. PageRank Brin, S. and Page, L. 1998. The
    anatomy of a large-scale hypertextual Web search
    engine. In WWW-7, 1998.
  • 10. HITS Kleinberg, J. M. 1998. Authoritative
    sources in a hyperlinked environment. SODA, 1998.

17
(IV)
  • Clustering
  • 11. K-Means MacQueen, J. B., Some methods for
    classification and analysis of multivariate
    observations, in Proc. 5th Berkeley Symp.
    Mathematical Statistics and Probability, 1967.
  • 12. BIRCH Zhang, T., Ramakrishnan, R., and
    Livny, M. 1996. BIRCH an efficient data
    clustering method for very large databases. In
    SIGMOD '96.
  • Bagging and Boosting
  • 13. AdaBoost Freund, Y. and Schapire, R. E.
    1997. A decision-theoretic generalization of
    on-line learning and an application to boosting.
    J. Comput. Syst. Sci. 55, 1 (Aug. 1997), 119-139.

18
(V)
  • Sequential Patterns
  • 14. GSP Srikant, R. and Agrawal, R. 1996.
    Mining Sequential Patterns Generalizations and
    Performance Improvements. In Proceedings of the
    5th International Conference on Extending
    Database Technology, 1996.
  • 15. PrefixSpan J. Pei, J. Han, B.
    Mortazavi-Asl, H. Pinto, Q. Chen, U. Dayal and
    M-C. Hsu. PrefixSpan Mining Sequential Patterns
    Efficiently by Prefix-Projected Pattern Growth.
    In ICDE '01.
  • Integrated Mining
  • 16. CBA Liu, B., Hsu, W. and Ma, Y. M.
    Integrating classification and association rule
    mining. KDD-98.

19
(VI)
  • Rough Sets
  • 17. Finding reduct Zdzislaw Pawlak, Rough Sets
    Theoretical Aspects of Reasoning about Data,
    Kluwer Academic Publishers, Norwell, MA, 1992
  • Graph Mining
  • 18. gSpan Yan, X. and Han, J. 2002. gSpan
    Graph-Based Substructure Pattern Mining. In ICDM
    '02.

20
Top-10 Algorithm Finally Selected at ICDM06
  • 1 C4.5 (61 votes)
  • 2 K-Means (60 votes)
  • 3 SVM (58 votes)
  • 4 Apriori (52 votes)
  • 5 EM (48 votes)
  • 6 PageRank (46 votes)
  • 7 AdaBoost (45 votes)
  • 7 kNN (45 votes)
  • 7 Naive Bayes (45 votes)
  • 10 CART (34 votes)

21
Conferences and Journals on Data Mining
  • KDD Conferences
  • ACM SIGKDD Int. Conf. on Knowledge Discovery in
    Databases and Data Mining (KDD)
  • SIAM Data Mining Conf. (SDM)
  • (IEEE) Int. Conf. on Data Mining (ICDM)
  • Conf. on Principles and practices of Knowledge
    Discovery and Data Mining (PKDD)
  • Pacific-Asia Conf. on Knowledge Discovery and
    Data Mining (PAKDD)

22
  • Other related conferences
  • ACM SIGMOD
  • VLDB
  • (IEEE) ICDE
  • WWW, SIGIR
  • ICML, CVPR, NIPS
  • Journals
  • Data Mining and Knowledge Discovery (DAMI or
    DMKD)
  • IEEE Trans. On Knowledge and Data Eng. (TKDE)
  • KDD Explorations
  • ACM Trans. on KDD

23
Why Not Traditional Data Analysis?(1)
  • Tremendous amount of data
  • Algorithms must be highly scalable to handle such
    as tera-bytes of data
  • High-dimensionality of data
  • Micro-array may have tens of thousands of
    dimensions

24
(2)
  • High complexity of data
  • Data streams and sensor data
  • Time-series data, temporal data, sequence data
  • Structure data, graphs, social networks and
    multi-linked data
  • Heterogeneous databases and legacy databases
  • Spatial, spatiotemporal, multimedia, text and Web
    data
  • Software programs, scientific simulations
  • New and sophisticated applications

25
Data warehouse
  • Modern organisations must respond quickly to any
    change in the market. This requires rapid access
    to current data normally stored in operational
    databases.
  • However, an organisation must also determine
    which trends are relevant. This task is
    accomplished with access to historical data that
    are stored in large databases called data
    warehouses.

26
  • The main characteristic of a data warehouse is
    its capacity. A data warehouse is really big
    it includes millions, even billions, of data
    records.
  • The data stored in a data warehouse is
  • time dependent linked together by the times of
    recording and
  • integrated all relevant information from the
    operational databases is combined and structured
    in the warehouse.

27
Query tools
  • A data warehouse is designed to support
    decision-making in the organisation. The
    information needed can be obtained with query
    tools.
  • Query tools are assumption-based a user must
    ask the right questions.

28
How is data mining applied in practice?
  • Many companies use data mining today, but refuse
    to talk about it.
  • In direct marketing, data mining is used for
    targeting people who are most likely to buy
    certain products and services.
  • In trend analysis, it is used to determine trends
    in the marketplace, for example, to model the
    stock market. In fraud detection, data mining is
    used to identify insurance claims, cellular phone
    calls and credit card purchases that are most
    likely to be fraudulent.

29
  • Motivation Finding latent relationships in data
  • What products were often purchased together?
    Beer and diapers?!
  • What are the subsequent purchases after buying a
    PC?
  • What kinds of DNA are sensitive to this new drug?
  • Can we automatically classify web documents?

30
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  • Applications
  • Market basket data analysis (shelf space
    planning/increasing sales/promotion)
  • cross-marketing
  • catalog design
  • sale campaign analysis
  • Web log (click stream) analysis
  • DNA sequence analysis

32
Data mining tools
Data mining is based on intelligent technologies
already discussed in this book. It often applies
such tools as neural networks and neuro-fuzzy
systems. However, the most popular tool used
for data mining is a decision tree.
33
Decision trees
A decision tree can be defined as a map of the
reasoning process. It describes a data set by a
tree-like structure. Decision trees are
particularly good at solving classification
problems.
34
ID3
  • (tall, blond, blue) w
  • (short, silver, blue) w
  • (short, black, blue) w
  • (tall, blond, brown) w
  • (tall, silver, blue) w
  • (short, blond, blue) w
  • (short, black, brown) e
  • (tall, silver, black) e
  • (short, black, brown) e
  • (tall, black, brown) e
  • (tall, black, black) e
  • (short, blond, black) e

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  • A decision tree consists of nodes, branches and
    leaves.
  • The top node is called the root node. The tree
    always starts from the root node and grows down
    by splitting the data at each level into new
    nodes. The root node contains the entire data
    set (all data records), and child nodes hold
    respective subsets of that set.
  • All nodes are connected by branches.
  • Nodes that are at the end of branches are called
    terminal nodes, or leaves.

40
How does a decision tree select splits?
  • A split in a decision tree corresponds to the
    predictor with the maximum separating power. The
    best split does the best job in creating nodes
    where a single class dominates.
  • One of the best known methods of calculating the
    predictors power to separate data is based on
    the Gini coefficient of inequality.

41
Major Issues in Data Mining(1)
  • Mining methodology
  • Mining different kinds of knowledge from diverse
    data types, e.g., bio, stream, Web
  • Performance efficiency, effectiveness, and
    scalability
  • Pattern evaluation the interestingness problem
  • Incorporation of background knowledge
  • Handling noise and incomplete data
  • Parallel, distributed and incremental mining
    methods
  • Integration of the discovered knowledge with
    existing one knowledge fusion

42
(2)
  • User interaction
  • Data mining query languages and ad-hoc mining
  • Expression and visualization of data mining
    results
  • Interactive mining of knowledge at multiple
    levels of abstraction
  • Applications and social impacts
  • Domain-specific data mining invisible data
    mining
  • Protection of data security, integrity, and
    privacy

43
Summary(1)
  • Data mining Discovering interesting patterns
    from large amounts of data
  • A natural evolution of database technology, in
    great demand, with wide applications
  • A KDD process includes data cleaning, data
    integration, data selection, transformation, data
    mining, pattern evaluation, and knowledge
    presentation

44
(2)
  • Mining can be performed in a variety of
    information repositories
  • Data mining functionalities characterization,
    discrimination, association, classification,
    clustering, outlier and trend analysis, etc.
  • Data mining systems and architectures
  • Major issues in data mining

45
  • Thank you

46
An example of a decision tree
47
The Gini coefficient
The Gini coefficient is a measure of how well
the predictor separates the classes contained in
the parent node. Gini, an Italian economist,
introduced a rough measure of the amount of
inequality in the income distribution in a
country.
48
Computation of the Gini coefficient
The Gini coefficient is calculated as the area
between the curve and the diagonal divided by the
area below the diagonal. For a perfectly equal
wealth distribution, the Gini coefficient is
equal to zero.
49
Selecting an optimal decision tree (a) Splits
selected by Gini
50
Selecting an optimal decision tree (b) Splits
selected by guesswork
51
Gain chart of Class A
52
Can we extract rules from a decision tree?
  • The pass from the root node to the bottom leaf
    reveals a decision rule.
  • For example, a rule associated with the right
    bottom leaf in the figure that represents Gini
    splits can be represented as follows
  • if (Predictor 1 no)
  • and (Predictor 4 no)
  • and (Predictor 6 no)
  • then class Class A

53
Case study Profiling people with high blood
pressure
A typical task for decision trees is to
determine conditions that may lead to certain
outcomes. Blood pressure can be categorised as
optimal, normal or high. Optimal pressure is
below 120/80, normal is between 120/80 and
130/85, and a hypertension is diagnosed when
blood pressure is over 140/90.
54
A data set for a hypertension study
55
A data set for a hypertension study (continued)
56
Data cleaning
Decision trees are as good as the data they
represent. Unlike neural networks and fuzzy
systems, decision trees do not tolerate noisy and
polluted data. Therefore, the data must be
cleaned before we can start data mining. We
might find that such fields as Alcohol
Consumption or Smoking have been left blank or
contain incorrect information.
57
Data enriching
From such variables as weight and height we can
easily derive a new variable, obesity. This
variable is calculated with a body-mass index
(BMI), that is, the weight in kilograms divided
by the square of the height in metres. Men with
BMIs of 27.8 or higher and women with BMIs of
27.3 or higher are classified as obese.
58
A data set for a hypertension study (continued)
59
Growing a decision tree
60
Growing a decision tree (continued)
61
Growing a decision tree (continued)
62
Solution space of the hypertension study
The solution space is first divided into four
rectangles by age, then age group 51-64 is
further divided into those who are overweight and
those who are not. And finally, the group of
obese people is divided by race.
63
Solution space of the hypertension study
64
Hypertension study forcing a split
65
Advantages of decision trees
  • The main advantage of the decision-tree approach
    to data mining is it visualises the solution it
    is easy to follow any path through the tree.
  • Relationships discovered by a decision tree can
    be expressed as a set of rules, which can then be
    used in developing an expert system.

66
Drawbacks of decision trees
  • Continuous data, such as age or income, have to
    be grouped into ranges, which can unwittingly
    hide important patterns.
  • Handling of missing and inconsistent data
    decision trees can produce reliable outcomes only
    when they deal with clean data.
  • Inability to examine more than one variable at a
    time. This confines trees to only the problems
    that can be solved by dividing the solution space
    into several successive rectangles.

67
In spite of all these limitations, decision
trees have become the most successful technology
used for data mining. An ability to produce
clear sets of rules make decision trees
particularly attractive to business professionals.
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