Introduction Introduction to Data Mining with Case Studies Author: G. K. Gupta Prentice Hall India, 2006

Introduction

Introduction to Data Mining with Case StudiesAuthor: G. K. Gupta

Prentice Hall India, 2006.

27 November 2008 ©GKGupta 2

• What is data mining?• Why data mining?• What applications? • What techniques?• What process?• What software?

Objectives


Definition

Data mining may be defined as follows:

data mining is a collection of techniques for efficient automated discovery of previously unknown, valid, novel, useful and understandable patterns in large databases. The patterns must be actionable so they may be used in an enterprise’s decision making.


What is Data Mining?

• Efficient automated discovery of previously unknown patterns in large volumes of data.

• Patterns must be valid, novel, useful and understandable.

• Businesses are mostly interested in discovering past patterns to predict future behaviour.

• A data warehouse, to be discussed later, can be an enterprise’s memory. Data mining can provide intelligence using that memory.


Examples

• amazon.com uses associations. Recommendations to customers are based on past purchases and what other customers are purchasing.

• A store in USA “Just for Feet” has about 200 stores, each carrying up to 6000 shoe styles, each style in several sizes. Data mining is used to find the right shoes to stock in the right store.

• More examples in case studies to be discussed later.


Data Mining

• We assume we are dealing with large data, perhaps Gigabytes, perhaps in Terabytes.

• Although data mining is possible with smaller amount of data, bigger the data, higher the confidence in any unknown pattern that is discovered.

• There is considerable hype about data mining at the present time and Gartner Group has listed data mining as one of the top ten technologies to watch.

Question: How many books could one store in one Terabyte of memory?


• Growth in generation and storage of corporate data – information explosion

• Need for sophisticated decision making – current database systems are Online Transaction Processing (OLTP) systems. The OLTP data is difficult to use for such applications. Why?

• Evolution of technology – much cheaper storage, easier data collection, better database management, to data analysis and understanding.

Why Data Mining Now?


• Database systems are being used since the 1960s in the Western countries (perhaps since 1980s in India). These systems have generated mountains of data.

• Point of sale terminals and bar codes on many products, railway bookings, educational institutions, huge number of mobile phones, electronic commerce, all generate data.

• Government is now collecting a lot of information.

Information explosion


• Internet banking via networked computers and ATMs.

• Credit and debit cards.• Medical data, doctors, hospitals.• Transportation, Indian railways, automatic toll

collection on toll roads, growing air travel.• Passports, NRI visas, Other visas, NRI money

transfers.

Question: Can you think of other examples of data collection?



Many adults in India generate:• Mobile phone transactions. More than 300 million

phones in India, reportedly growing at the rate of 10,000 new ones every hour! Mobile companies must save information about calls.

• Growing middle class with growing number of credit and debit card transactions. About 25m credit cards and 70m debit cards in 2007. Annual growth rate about 30% and 40% respectively. Could be 55m credit cards and 200m debit cards in 2010 resulting in perhaps 500m transactions annually.



• India has some huge enterprises, for example Indian railways, perhaps the busiest network in the world with 2.5m employees, 10,000 locomotives, 10,000 passenger trains daily, 10,000 freight trains daily and 20m passengers daily.

• Growing airline traffic with more than ten airlines. Perhaps 30m passengers annually.

• Growing number of motor vehicles – registration, insurance, driver license

• Internet surfing records



OLTPAs noted earlier, most enterprise database systems were designed in the 1970’s or 1980’s and were mainly designed to automate some of the office procedures e.g. order entry, student enrolment, patient registration, airline reservations. These are well structured repetitive operations easily automated.


• Need for business memory and intelligence.• Need to serve customers better by learning from

past interactions.• OLTP data is not a good basis for maintaining an

enterprise memory.• The intelligence hidden in data could be the secret

weapon in a competitive business world but given the information explosion not even a small fraction could be looked at by human eye.

Question: Why OLTP is not good for maintaining an enterprise memory?

Decision Making


OLTP vs Decision Making

Clerical view of data focuses on details required for day-to-day running of an enterprise.

Management view of data focuses on summary data to identify trends, challenges and opportunities.

The detailed data view is the operational view while the management view is decision-support view. Comparison of the two views:


Operational vs Management View

Operational Decision-Support

Users – Admin staff Users – Management

Day–to–day work Decision support

Application oriented Subject oriented

Current data Historical data

Detailed Overall view – summaries

Simple queries Complex queries

Predetermined queries Ad hoc queries

Update/Select Only Select

Real–time Not real–time


Evolution of Technology• Corporate data growth accompanied by decline in

the cost of storage and processing. • PC motherboard performance, measured in MHz/$,

is currently doubling every 27 ± 2 months. • Next slide using logarithmic scale shows that disk

is now about 10GB per US dollar and the following slide shows that sales of disk storage is growing exponentially.

• Look at computing trends at http://www.zoology.ubc.ca/~rikblok/ComputingTrends/

Question: How much is the cost of 100GB disk? What is the cost of a PC and what is its CPU performance?

http://www.zoology.ubc.ca/~rikblok/ComputingTrends/

http://www.zoology.ubc.ca/~rikblok/ComputingTrends/


Decline in Hard Drive cost


Growth in Worldwide Disk Capacity

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1996 1997 1998 1999 2000 2001 2002 2003

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Evolution of Technology

Question: What do the graphs in the last two slides tell us? What scales are used in them? What was the pink line is the first graph?


Evolution of Technology

• Database technology has improved over the years.

• Data collection is often much better and cheaper now

• The need for analyzing and synthesizing information is growing in a fiercely competitive business environment of today.


New applications

Sophisticated applications of modern enterprises include:

- sales forecasting and analysis- marketing and promotion planning- business modeling

OLTP is not designed for such applications. Also, large enterprises operate a number of database systems and then it is necessary to integrate information for decision making applications.

Question: Why OLTP cannot be used for sales forecasting and analysis?


Why Data Mining Now?As noted earlier, the reasons may be summarized as:

•Accumulation of large amounts of data• Increased affordable computing power enabling data mining processing

• Statistical and learning algorithms• Availability of software• Strong business competition


Large amount of data

Already discussed that many enterprises have large amounts of data accumulated over 30+ years.

Noted earlier that some enterprises collect information for analysis, for example, supermarkets in USA offer loyalty cards in exchange for shopper information. Loyalty cards in Australia also collect information using a reward system.


Growth of cards

A recent survey in USA found that the percentages of US adults using the following types of cards were:

• Credit cards - 88%;• ATM cards - 60%• Membership cards - 58%• Debit cards - 35%• Prepaid cards - 35%• Loyalty cards - 29%

Question: What kind of data do these cards generate?


Affordable computing power

Data mining is usually computationally intensive. Dramatic reduction in the price of computer systems, as noted earlier, is making it possible to carry out data mining without investing huge amounts of resources in hardware and software.

In spite of affordable computing power, using data mining can be resources intensive.


Algorithms

A variety of statistical and learning algorithms have been available in fields like statistics and artificial intelligence that have been adapted for data mining.

With new focus on data mining, new algorithms are being developed.


Availability of Software

Large variety of DM software is now available. Some more widely used software is:

• IBM - Intelligent Miner and more• SAS - Enterprise Miner• Silicon Graphics - MineSet• Oracle - Thinking Machines - Darwin• Angoss - knowledgeSEEKER


Strong Business Competition

Growth in service economies. Almost every business is a service business. Service economies are information rich and very competitive.

Consider the telecommunications environment in Australia. About 20 years ago, Telstra was a monopoly. The field is now very competitive. Mobile phone market in India is also very competitive.


Applications

In finance, telecom, insurance and retail:– Loan/credit card approval– market segmentation– fraud detection– better marketing– trend analysis– market basket analysis– customer churn– Web site design and promotion


Loan/Credit card approvals

In a modern society, a bank does not know its customers. Only knowledge a bank has is their information stored in the computer.

Credit agencies and banks collect a lot of customers’ behavioural data from many sources. This information is used to predict the chances of a customer paying back a loan.


Market Segmentation

• Large amounts of data about customers contains valuable information

• The market may be segmented into many subgroups according to variables that are good discriminators

• Not always easy to find variables that will help in market segmentation


Fraud Detection

• Very challenging since it is difficult to define characteristics of fraud. Often based on detecting changes from the norm.

• In statistics, it is common to throw out the outliers but in data mining it may be useful to identify them since they could either be due to errors or perhaps fraud.


Better Marketing

When customers buy new products, other products may be suggested to them when they are ready.As noted earlier, in mail order marketing for example, one wants to know:

- will the customer respond?- will the customer buy and how much?- will the customer return purchase?- will the customer pay for the purchase?


Better Marketing

It has been reported that more than 1000 variable values on each customer are held by some mail order marketing companies.

The aim is to “lift” the response rate.


Trend analysis

In a large company, not all trends are always visible to the management. It is then useful to use data mining software that will identify trends.

Trends may be long term trends, cyclic trends or seasonal trends.


Market Basket Analysis

• Aims to find what the customers buy and what they buy together

• This may be useful in designing store layouts or in deciding which items to put on sale

• Basket analysis can also be used for applications other than just analysing what items customers buy together


Customer Churn• In businesses like telecommunications,

companies are trying very hard to keep their good customers and to perhaps persuade good customers of their competitors to switch to them.

• In such an environment, businesses want to find which customers are good, why customers switch and what makes customers loyal.

• Cheaper to develop a retention plan and retain an old customer than to bring in a new customer.


Customer Churn

• The aim is to get to know the customers better so you will be able to keep them longer.

• Given the competitive nature of businesses, customers will move if not looked after.

• Also, some businesses may wish to get rid of customers that cost more than they are worth e.g. credit card holders that don’t use the card, bank customers with very small amount of money in their accounts.


Web site design

• A Web site is effective only if the visitors easily find what they are looking for.

• Data mining can help discover affinity of visitors to pages and the site layout may be modified based on this information.


Data Mining ProcessSuccessful data mining involves careful determining the aims and selecting appropriate data. The following steps should normally be followed:

1. Requirements analysis 2. Data selection and collection3. Cleaning and preparing data4. Data mining exploration and validation5. Implementing, evaluating and monitoring6. Results visualisation


Requirements Analysis

The enterprise decision makers need to formulate goals that the data mining process is expected to achieve. The business problem must be clearly defined. One cannot use data mining without a good idea of what kind of outcomes the enterprise is looking for.

If objectives have been clearly defined, it is easier

to evaluate the results of the project.


Data Selection and Collection

Find the best source databases for the data that is required. If the enterprise has implemented a data warehouse, then most of the data could be available there. Otherwise source OLTP systems need to be identified and required information extracted and stored in some temporary system. In some cases, only a sample of the data available may be required.


Cleaning and Preparing Data

This may not be an onerous task if a data warehouse containing the required data exists, since most of this must have already been done when data was loaded in the warehouse. Otherwise this task can be very resource intensive, perhaps more than 50% of effort in a data mining project is spent on this step. Essentially a data store that integrates data from a number of databases may need to be created. When integrating data, one often encounters problems like identifying data, dealing with missing data, data conflicts and ambiguity. An ETL (extraction, transformation and loading) tool may be used to overcome these problems.


Exploration and Validation

Assuming that the user has access to one or more data mining tools, a data mining model may be constructed based on the enterprise’s needs. It may be possible to take a sample of data and apply a number of relevant techniques. For each technique the results should be evaluated and their significance interpreted. This is likely to be an iterative process which should lead to selection of one or more techniques that are suitable for further exploration, testing and validation.


Implementing, Evaluating and Monitoring

Once a model has been selected and validated, the model can be implemented for use by the decision makers. This may involve software development for generating reports or for results visualisation and explanation for managers. If more than one technique is available for the given data mining task, it is necessary to evaluate the results and choose the best. This may involve checking the accuracy and effectiveness of each technique.


Implementing, Evaluating and Monitoring

Regular monitoring of the performance of the techniques that have been implemented is required. Every enterprise evolves with time and so must the data mining system. Monitoring may from time to time to lead to the refinement of tools and techniques that have been implemented.


Results Visualisation

Explaining the results of data mining to the decision makers is an important step. Most DM software includes data visualisation modules which should be used in communicating data mining results to the managers. Clever data visualisation tools are being developed to display results that deal with more than two dimensions. The visualisation tools available should be tried and used if found effective for the given problem.


Data Mining Process – Another Approach

The last few slides presented one approach.

Another approach that also includes six steps has been proposed by CRISP–DM (Cross–Industry Standard Process for Data Mining) developed by an industry consortium.The six steps are:


CRISP–DM Steps

The six CRISP–DM steps are:1. Business understanding2. Data understanding3. Data preparation4. Modelling5. Evaluation6. Deployment


CRISP–DM Steps

The six steps proposed in CRISP–DM are similar to the six steps proposed earlier.. The CRIS–DM steps are shown in the following figure.

Question: Compare the two sets of steps, one given in previous few slides and the CRISP-DM approach. Which approach is better?


CRISP Data Mining Model


Data Mining Techniques

• Although data mining is a new field, it uses many techniques developed years ago in other fields

• Machine learning, statistics, artificial intelligence, etc

• These techniques are in some cases modified to deal with large amounts of data


Data Mining Techniques

Data mining includes a large number of techniques including concept/class description, association analysis, classification and prediction, cluster analysis, outlier analysis etc.

Expression and visualization of data mining results is a challenging task.

Privacy issues also need to be considered.


Data Mining Tasks

• Association analysis• Classification and prediction• Cluster analysis• Web data mining• Search Engines• Data warehouse and OLAP• Others, for example, Sequential patterns and

Time-series analysis, not covered in this book


Association Analysis

• Association analysis involves discovery of relationships or correlations among a set of items.

• Discovering that personal loans are repaid with 80% confidence when the person owns his home.

• The classical example is the one where a store discovered that people buying nappies tend also to buy beer.


Associations

The association rules are often written as X → Y meaning that whenever X appears Y also tends to appear. X and Y may be collection of attributes.

A supermarket like Woolworths may have several thousand items and many millions of transactions a week (i.e. Gigabytes of data each week). Note that the quantities of items bought is ignored.


Classification and Prediction

A set of training objects each with a number of attribute values are given to the classifier. The classifier formulates rules for each class in the training set so that the rules may be used to classify new objects. Some techniques do not require training data.

Classification may be used for predicting the class label of data objects. Number of techniques including decision tree and neural network.


Cluster Analysis

Similar to classification in that the aim is to build clusters such that each of them is similar within itself but is dissimilar to others. Clustering does not rely on class-labeled data objects.

Based on the principle of maximizing the intracluster similarity and minimizing the intercluster similarity.


Web data mining

The Web revolution has had a profound impact on the way we search and find information at home and at work. From its beginning in the early 1990s, the web has grown to more than ten billion pages in 2008 (estimates vary), perhaps even more by the time you are looking at this slide. Web usage, Web content and Web structure are discussed in Chapter 5.


Search engines

Normally the search engine databases of Web pages are built and updated automatically by Web crawlers. When one searches the Web using one of the search engines, one is not searching the entire Web. Instead one is only searching the database that has been compiled by the search engine. There are a number of challenging problems related to search engines that are discussed in Chapter 6 including how to assign a ranking to each Web page that is retrieved in response to a user query.


Data Warehousing and OLAP

Data warehousing is a process by which an enterprise collects data from the whole enterprise to build a single version of the truth. This information is useful for decision makers and may also be used for data mining. A data warehouse can be of real help in data mining since data cleaning and other problems of collecting data would have already been overcome.

OLAP (Online Analytical Processing) tools are decision support tools that are often built on top of a data warehouse or another database. OLAP goes further than traditional query and report tools in that a decision maker already has a hypothesis which he/she is trying to test.


Data Warehousing and OLAP

Data mining is somewhat different than OLAP since in data mining a hypothesis is not being tested. Instead data mining is used to uncover novel patterns in the data.


Before Data Mining

To define a data mining task, one needs to answer the following:

• What data set do I want to mine? • What kind of knowledge do I want to mine?• What background knowledge could be useful?• How do I measure if the results are interesting?• How do I display what I have discovered?


Task-relevant Data

The whole database may not be required since it may be that we only want to study something specific e.g. trends in postgraduate students

- countries they come from- degree program they are doing- their age?- time they take to finish the degree- scholarship they have they been awarded

May need to build a database subset before data mining can be done.


Task-relevant Data

Data collection is non-trivial.

OLTP data is not useful since it is changing all the time. In some cases, data from more than one database may be needed.


Preprocessing

• A data mining process would normally involve preprocessing

• Often data mining applications use data warehousing

• One approach is to pre-mine the data, warehouse it, then carry out data mining

• The process is usually iterative and can take years of effort for a large project


Data Preprocessing

• Preprocessing is very important although often considered too mundane to be taken seriously

• Preprocessing may also be needed after the data warehouse phase

• Data reduction may be needed to transform very high dimensional data to a lower dimensional data


Data Preprocessing

• Feature Selection• Use sampling?• Normalization• Smoothing• Dealing with duplicates, missing data• Dealing with time-dependent data


Background knowledge

Background information may be useful in the discovery process.

For example, concept hierarchies or relationships between data may be useful in data mining. For postgraduate degrees, we may wish to look at all Masters degrees and all doctorate degrees separately.


Measuring interest

Data mining process may generate many patterns. We cannot look at all of them and so need some way to separate uninteresting results from the interesting ones.

This may be based on simplicity of pattern, rule length, or level of confidence.


Visualization

We must be able to display results so that they are easy to understand.

Display may be a graph, pie chart, tables etc. Some displays are better than others for a given kind of knowledge.


Guidelines for Successful Data Mining

• The data must be available

• The data must be relevant, adequate and clean• There must be a well-defined problem• The problem should not be solvable by means of

ordinary query or OLAP tools• The results must be actionable



1. Use a small team with a strong internal integration and a loose management style.

2. Carry out a small pilot project before a major data mining project.

3. Identify a clear problem owner responsible for the project. Could be someone in a sales or marketing. This will benefit the external integration.

Question: Why each of the above guidelines is important for success?



4. Try to realise a positive return on investment within 6 to 12 months.

5. The whole data mining project should have the support of the top management of the company.

Question: Why each of the above guidelines is important for success?


Data Mining Software

As noted earlier, a large variety of DM software is now available. Some more widely used software is:

• IBM - Intelligent Miner and more• SAS - Enterprise Miner• Silicon Graphics - MineSet• Oracle - Thinking Machines - Darwin• Angoss - knowledgeSEEKER


Choosing Data Mining Software

Many factors need to be considered if purchasing significant software:

• Product and vendor information• Total cost of ownership• Performance• Functionality and modularity• Training and support• Reporting facilities and visualization• Usability

Question: Which one of the above is the most important? Why?


References

•D. Hand, H. Mannila and P. Smyth, Principles of Data Mining, MIT Press, 2001.

•J. Han and M. Kamber, Data Mining: Concepts and Techniques, Morgan Kaufmann, 2001. The Web site for this book is http://www.cs.sfu.ca/~han/DM_Book.

•I. H. Witten and E. Frank, Data Mining: Practical Machine Learning Tools and Techniques with Java Implementations, Morgan Kaufmann, 2000. The Web site for this book is www.mkp.com/datamining.

•Dhar, V. and Stein, R., 1997, Seven methods for transforming corporate data into business intelligence, Prentice Hall.


References

•U. M. Fayyad, G. Piatetsky-Shapiro, P. Smyth, and R. Uthurusamy (eds.), Advances in Knowledge Discovery and Data Mining, AAAI/MIT Press, 1996

•M.S. Chen, J. Han, and P.S. Yu, Data Mining: An Overview from a Database Perspective, IEEE Transactions on Knowledge and Data Engineering, 8(6), pp 866-883, 1996.

•Berry, M. and Linoff, G., 1997, Data mining techniques for marketing, sales and support, John Wiley & Sons.

•Berry, M. and Linoff, G., 1999, Mastering data mining, John Wiley & Sons.

Documents

Introduction Introduction to Data Mining with Case Studies Author: G. K. Gupta Prentice Hall India, 2006