Transcript Data Visualization

Chapter 3: Data Mining and
Data Visualization
Modern Data Warehousing, Mining,
and Visualization: Core Concepts
by George M. Marakas
© 2003, Prentice-Hall
Chapter 3 - 1
3-1: A Picture is Worth a
Thousand Words
Data mining is the set of activities used to find
new, hidden, or unexpected patterns in data.
These techniques are often called knowledge
data discovery (KDD), and include statistical
analysis, neural or fuzzy logic, intelligent
agents or data visualization.
The KDD techniques not only discover useful
patterns in the data, but also can be used to
develop predictive models.
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Verification Versus Discovery
In the past, decision support activities were
primarily based on the concept of verification.
This required a great deal of prior knowledge
on the decision-maker’s part in order to verify
a suspected relationship.
With the advance of technology, the concept
of verification began to turn into discovery.
© 2003, Prentice-Hall
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Data Mining’s Growth in Popularity
One reason is that we keep getting more and
more data all the time and need tools to
understand it.
We also are aware that the human brain has
trouble processing multidimensional data.
A third reason is that machine learning
techniques are becoming more affordable
and more refined at the same time.
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Making Accurate Predictions with
Data Mining
Although the literature contains
statements such as “data mining will
allow us to predict who will buy a
particular product,” that is against
human nature.
In situations where data mining is used
to predict response to a marketing
campaign, only about 5% of the people
selected as “likely respondents” actually
do respond.
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Making Accurate Predictions with
Data Mining (cont.)
Although the accuracy of predicting
individual behavior is not so good, it is
better than it seems, since direct
marketing efforts often have “hit rates”
of only about 1% without data mining.
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3-2: Online Analytical Processing
(OLAP)
Codd developed a set of 12 rules for the
development of multidimensional databases:
Multidimensional view
2. Transparent to user
3. Accessible
4. Consistent reporting
5. Client-server
architecture
6. Generic dimensionality
1.
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Dynamic sparse matrix
handling
8. Multiuser support
9. Cross-dimensional ops
10. Intuitive manipulation
11. Flexible reporting
12. Unlimited dimension and
aggregation
7.
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OLAP as Implemented
To date, it does not appear that any
implementation exists that satisfies all 12
rules.
Some people argue it might not even be
possible to attain all of them.
More recently, the term OLAP has come to
represent the broad category of software
technology that enables multidimensional
analysis of enterprise data.
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Multidimensional OLAP (MOLAP)
Data can be viewed
across several
dimensions. Here sales
are arrayed by region and
product.
A fourth dimension could
be added by using several
graphs -- perhaps at
different time points.
Most analyses have many
more dimensions than
this. MOLAP handles
data as an n-dimensional
hypercube.
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0.7
0.6
Sales
0.5
0.4
4
3
0.3
2
1
Region
Product
1
2
3
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Relational OLAP (ROLAP)
A large relational database server replaces
the multidimensional one.
The database contains both detailed and
summarized data, allowing “drill down”
techniques to be applied.
SQL interfaces allow vendors to build tools,
both portable and scalable.
This does require databases with many
relational tables which may lead to
substantial processor overhead on complex
joins.
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A Typical Relational Schema
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3-3: Techniques Used to Mine the Data
Paralleling the popularity of data mining itself,
the development of new techniques is
exploding as well.
Many innovations are vendor-specific, which
sometimes does little to advance the state of
the art.
Regardless, data-mining techniques tend to
fall into four major categories:
1. classification
2. association
3. sequencing
4. clustering
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Classification methods
The goal is to discover rules that define
whether an item belongs to a particular
subset or class of data.
For example, if we are trying to determine
which households will respond to a direct mail
campaign, we will want rules that separate
the “probables” from the not probables.
These IF-THEN rules often are portrayed in a
tree-like structure.
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Association Methods
These techniques search all transactions
from a system for patterns of occurrence.
A common method is market basket analysis,
in which the set of products purchased by
thousands of consumers are examined.
Results are then portrayed as percentages;
for example, “30% of the people that buy
steaks also buy charcoal”.
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Sequencing Methods
These methods are applied to time series
data in an attempt to find hidden trends.
If found, these can be useful predictors of
future events.
For example, customer groups that tend to
purchase products tied-in with hit movies
would be targeted with promotional
campaigns timed to release dates.
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Clustering Techniques
Clustering techniques attempt to create
partitions in the data according to some
distance metric.
The clusters formed are data grouped
together simply by their similarity to their
neighbors.
By examining the characteristics of each
cluster, it may be possible to establish rules
for classification.
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Data Mining Technologies
Statistics – the most mature data mining
technologies, but are often not applicable
because they need clean data. In addition,
many statistical procedures assume linear
relationships, which limits their use.
Neural networks, genetic algorithms, fuzzy
logic – these technologies are able to work
with complicated and imprecise data. Their
broad applicability has made them popular in
the field.
© 2003, Prentice-Hall
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Data Mining Technologies (cont.)
Decision trees – these technologies are
conceptually simple and have gained in
popularity as better tree growing
software was introduced. Because of
the way they are used, they are perhaps
better called “classification” trees.
© 2003, Prentice-Hall
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The Knowledge Discovery
Search Process
Table 3-2 contains a more detailed outline
of the process, but the major steps are:
 Define the business problem and
obtain the data to study it.
 Use data mining software to model
the problem.
 Mine the data to search for patterns
of interest.
© 2003, Prentice-Hall
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The Knowledge Discovery
Search Process (cont.)
 Review
the mining results and refine
them by respecifying the model.
 Once validated, make the model
available to other users of the DW.
© 2003, Prentice-Hall
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Creating a Data-Mining Model
Although syntax differs from vendor to vendor,
building a model on top of a database is much
like creating a table:
CREATE MODEL mail_list
Income character input, Age integer input, Respond
character input
To populate it with data, use an SQL INSERT:
INSERT INTO mail_list
SELECT income, age, respond
FROM client_list
WHERE region = ‘Southeast”
© 2003, Prentice-Hall
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Creating a Data-Mining Model (cont.)
The process automatically created additional views
of the model (mail_list_UNDERSTAND and
mail_list_PREDICT). These can be examined:
SELECT * FROM mail_list_UNDERSTAND
WHERE input_column_name = ‘income” and
input_column_value = “high” and
output_column_name = “respond” and
output_column_value = ‘yes”
Once these are created, they are treated as tables in
the database so they can be viewed and joined by
other users.
© 2003, Prentice-Hall
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New Applications for Data Mining
As the technology matures, new applications
emerge, especially in two new categories,
text mining and web mining. Some text
mining examples are:
 Distilling the meaning of a text
 Accurate summarization of a text
 Explication of the text theme structure
 Clustering of texts
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Web mining
Web mining is a special case of text mining
where the mining occurs over a website.
It enhances the website with intelligent
behavior, such as suggesting related links or
recommending new products.
It allows you to unobtrusively learn the
interests of the visitors and modify their user
profiles in real time.
They also allow you to match resources to the
interests of the visitor.
© 2003, Prentice-Hall
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3-4: Market Basket Analysis: The King of
Algorithms
This is the most widely used and, in many
ways, most successful data mining algorithm.
It essentially determines what products people
purchase together.
Stores can use this information to place these
products in the same area.
Direct marketers can use this information to
determine which new products to offer to their
current customers.
Inventory policies can be improved if reorder
points reflect the demand for the
complementary products.
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Association Rules for
Market Basket Analysis
Rules are written in the form “left-hand side
implies right-hand side” and an example is:
Yellow Peppers IMPLIES Red Peppers, Bananas, Bakery
To make effective use of a rule, three numeric
measures about that rule must be considered:
(1) support, (2) confidence and (3) lift
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Measures of Predictive Ability
Support refers to the percentage of baskets
where the rule was true (both left and right
side products were present).
2. Confidence measures what percentage of
baskets that contained the left-hand product
also contained the right.
3. Lift measures how much more frequently the
left-hand item is found with the right than
without the right.
1.
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An Example
Rule:
Green
Peppers
IMPLIES
Bananas
Red Peppers
IMPLIES
Bananas
Yellow
Peppers
IMPLIES
Bananas
Lift
1.37
1.43
1.17
Support
3.77
8.58
22.12
Confidence
85.96
89.47
73.09
The confidence suggests people buying any
kind of pepper also buy bananas.
Green peppers sell in about the same
quantities as red or yellow, but are not as
predctive.
© 2003, Prentice-Hall
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Market Basket Analysis Methodology
We first need a list of transactions and what
was purchased. This is pretty easily obtained
these days from scanning cash registers.
Next, we choose a list of products to analyze,
and tabulate how many times each was
purchased with the others.
The diagonals of the table shows how often a
product is purchased in any combination, and
the off-diagonals show which combinations
were bought.
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A Convenience Store Example
(5 transactions)
Consider the following simple example about
five transactions at a convenience store:
Transaction 1:
Transaction 2:
Transaction 3:
Transaction 4:
Transaction 5:
Frozen pizza, cola, milk
Milk, potato chips
Cola, frozen pizza
Milk, pretzels
Cola, pretzels
These need to be cross tabulated and displayed
in a table.
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A Convenience Store Example (5 transactions)
Product
Bought
Pizza
also
Milk
also
Cola
also
Chips
also
Pretzels
also
Pizza
2
1
2
0
0
Milk
1
3
1
1
1
Cola
2
1
3
0
1
Chips
0
1
0
1
0
Pretzels
0
1
1
0
2
Pizza and Cola sell together more often than
any other combo; a cross-marketing
opportunity?
Milk sells well with everything – people
probably come here specifically to buy it.
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Using the Results
The tabulations can immediately be
translated into association rules and the
numerical measures computed.
Comparing this week’s table to last week’s
table can immediately show the effect of this
week’s promotional activities.
Some rules are going to be trivial (hot dogs
and buns sell together) or inexplicable (toilet
rings sell only when a new hardware store is
opened).
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Limitations to Market Basket Analysis
A large number of real transactions are
needed to do an effective basket analysis, but
the data’s accuracy is compromised if all the
products do not occur with similar frequency.
The analysis can sometimes capture results
that were due to the success of previous
marketing campaigns (and not natural
tendencies of customers).
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Performing Analysis with Virtual Items
The sales data can be augmented with the
addition of virtual items. For example, we
could record that the customer was new to
us, or had children.
The transaction record might look like:
Item 1: Sweater
Item 2: Jacket
Item 3: New
This might allow us to see what patterns new
customers have versus old customers.
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Computing Measures of Association
Pizza
Milk
Cola
Chips
Pretzels
Pizza
2
1
2
0
0
Milk
1
3
1
1
1
Cola
2
1
3
0
1
Chips
0
1
0
1
0
Pretzels
0
1
1
0
2
Let’s do some of the textbook’s example
computations here ……
© 2003, Prentice-Hall
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Taxonomies
The presence of items not purchased very
frequently is an obstacle to a good market
basket analysis.
One way to deal with this is to eliminate
products that occur with a frequency less than
some threshold.
A better idea would be to try to form groups of
products that fall below the threshold. Four
flavors of popsicle occur 9% of the time all
together, but no more than 3% individually.
© 2003, Prentice-Hall
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Multidimensional Market
Basket Analysis
Rules can involve more than two items, for
example Plant and Clay Pot IMPLIES Soil.
These rules are built iteratively. First, pairs
are found, then relevant sets of three or four.
These are then pruned by removing those
that occur infrequently.
In an environment like a grocery store, where
customers commonly buy over 100 items,
rules could involve as many as 10 items.
© 2003, Prentice-Hall
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3-5: Current Limitations and
Challenges to Data Mining
Despite the potential power and value, data
mining is still a new field. Some things that
that thus far have limited advancement are:
 Identification of missing information – not
all knowledge gets stored in a database
 Data noise and missing values – future
systems need better ways to handle this
 Large databases and high dimensionality –
future applications need ways to partition
data into more manageable chunks
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3-6: Data Visualization:
“Seeing” the Data
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Visual Presentation
For any kind of high dimensional data set,
displaying predictive relationships is a
challenge.
The picture on the previous slide uses 3-D
graphics to portray the weather balloon data
numbers in text Table 11-4. We learn very
little from just examining the numbers .
Shading is used to represent relative degrees
of thunderstorm activity, with the darkest
regions the heaviest activity.
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A Bit of History
An early effort used sequences of twodimensional graphs to add depth.
Current virtual reality programs allow the user
to step through a data set. Try going to a
realtor’s website and taking a tour of a house
up for sale.
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Human Visual Perception and
Data Visualization
Data visualization is so powerful because the
human visual cortex converts objects into
information so quickly.
The next three slides show (1) usage of
global private networks, (2) flow through
natural gas pipelines, and (3) a risk analysis
report that permits the user to draw an
interactive yield curve.
All three use height or shading to add
additional dimensions to the figure.
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Global Private Network Activity
High Activity
Low Activity
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Natural Gas Pipeline Analysis
Note: Height shows total flow through compressor stations.
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An “Enlivened” Risk Analysis Report
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Geographical Information Systems
A GIS is a special purpose database that
contains a spatial coordinate system. A
comprehensive GIS requires:
1. Data input from maps, aerial photos, etc.
2. Data storage, retrieval and query
3. Data transformation and modeling
4. Data reporting (maps, reports and plans)
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The Special Capabilities of a GIS
In general, a GIS contains two types of data:
Spatial data: these elements correspond to a
uniquely-defined location on earth. They
could be in point, line or polygon form.
Attribute data: These are the data that will
be portrayed at the geographic
references established by spatial data.
Example: Data from an opinion poll is
displayed for multiple regions in the United
States. Clicking on an area allows the user
to drill down to the results for smaller areas.
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Telephone Polling Results
Note: On the “live” map, clicking on an area allows the user
to drill down and see results for smaller areas.
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3-7: Siftware Technologies
Although data visualization product vendors
seem to enter or leave the market with great
frequency, several firms are beginning to
develop significant brand loyalty.
Red Brick – Helped category managers at
H.E.B. in San Antonio to determine which
products to put in which stores. Another
application was the consolidation of three old
data warehouses at Hewlett-Packard.
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Siftware -- Continued
Oracle – A large suite of connectivity products
allows transparent access to mainframe
databases. Some major customers include
John Alden Insurance, ShopKo Stores and
Pacific Bell.
Informix – Associated Grocers uses Informix
data warehousing products at the heart of its
three-tier client-server system.
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Siftware -- Continued
Sybase – Sybase Warehouse WORKS is an
integrated system designed around the four
key functions in data warehousing.
Silicon Graphics – Data mining software is
mated to 3-D visualization tools to allow users
to fly through data.
IBM – provides a number of decision support
tools in its Information Warehouse Solutions.
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