chap1_intro.ppt

© Tan,Steinbach, Kumar Introduction to Data Mining 4/18/2004 ‹#›
Data Mining: Introduction
Lecture Notes for Chapter 1
Introduction to Data Mining
by
Dr. Muntadher Khamees

We are drowning in data,
but starving for
knowledge

 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)
Why Mine Data? Commercial Viewpoint

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

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
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
3,500,000
4,000,000
1995 1996 1997 1998 1999
The Data Gap
Total new disk (TB) since 1995
Number of
analysts
From: R. Grossman, C. Kamath, V. Kumar, “Data Mining for Scientific and 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

What is (not) Data Mining?
 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,)
 What is not Data
Mining?
– Look up phone
number in phone
directory
– Query a Web
search engine for
information about
“Amazon”

 Draws ideas from machine learning/AI, pattern
recognition, statistics, and database systems
 Traditional Techniques
may be unsuitable due to
– High dimensionality
of data
– Heterogeneous,
distributed nature
of data
Origins of Data Mining
Machine Learning/
Pattern
Recognition
Statistics/
AI
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.
From [Fayyad, et.al.] Advances in Knowledge Discovery and Data Mining, 1996

Data Mining Tasks...
 Classification [Predictive]
 Clustering [Descriptive]
 Association Rule Discovery [Descriptive]
 Regression [Predictive]

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 Example
Tid Refund Marital
Status
Taxable
Income Cheat
1 Yes Single 125K No
2 No Married 100K No
3 No Single 70K No
4 Yes Married 120K No
5 No Divorced 95K Yes
6 No Married 60K No
7 Yes Divorced 220K No
8 No Single 85K Yes
9 No Married 75K No
10 No Single 90K Yes
10
Refund Marital
Status
Taxable
Income Cheat
No Single 75K ?
Yes Married 50K ?
No Married 150K ?
Yes Divorced 90K ?
No Single 40K ?
No Married 80K ?
10
Test
Set
Training
Set
Model
Learn
Classifier

Classification Example

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

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.

Clustering Example

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

Comparing Clustering and Classification

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
1 Bread, Coke, Milk
2 Beer, Bread
3 Beer, Coke, Diaper, Milk
4 Beer, Bread, Diaper, Milk
5 Coke, Diaper, Milk
Rules Discovered:
{Milk} --> {Coke}
{Diaper, Milk} --> {Beer}

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.
 Comparing Regression and Classification
Property Classification Regression
Output type Discrete continuous
What are goes to
training to find
Decision boundary Best fit line
Evaluation Accuracy r2,(sum of square error )

Anomaly/Outlier Detection

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

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