1 18 April 2007 vizNET-LEEDS-PRES-0002-070418 A Rough Guide to Data Visualization – Part 2 VizNET...

1

18 April 2007

vizNET-LEEDS-PRES-0002-070418

A Rough Guide to Data Visualization – Part 2

VizNET 2007 Annual Event

Ken BrodlieSchool of ComputingUniversity of Leeds

2

18 April 2007


Outline of Session Visualizing Tables of Information

Scatter plot matrices Parallel coordinates Glyphs

Visualizing Structures of Information Interacting with a Visualization

Focus and context

Visualizing Time

3

18 April 2007


Visualizing Tables of Information

Multivariate datasets

4

18 April 2007


Data Tables Multivariate datasets can be

expressed as a data table Each entry in table is an

observation An observation consists of

values of a set of variables, or variates

A B C

1 .. .. ..

2 .. .. ..

variables

observations

5

18 April 2007


What are these?

6

18 April 2007


Multivariate Visualization

Example of iris data set 150 observations of 4

variables (length, width of petal and sepal)

Check wikipedia for explanations of petals & sepals

Techniques aim to display relationships between variables – the analytical task

Challenge in visualization is to design the visualization to match the analytical task

7

18 April 2007


Scatter Plot For two variates, we have

already met the scatter plot technique

It is useful for showing what happens to one variable as another changes…

8

18 April 2007


Scatter Plot Matrix – Iris Data Set

For a data table of N > 2variables, we can lookat all pairs of variables in a matrix of scatterplots.

What can you observe?

9

18 April 2007


Parallel Coordinates – Iris Data One axis per variable

Scaled to range Each observation is

plotted as a ‘polyline’ Correlations may start

to appear

10

18 April 2007


Parallel Coordinates Concept due to Alfred Inselberg Conceived the idea as a

research student in 1959… … idea gradually refined over

next 40 years

http://www.math.tau.ac.il/~aiisreal/

11

18 April 2007


The Screen Space Problem

All techniques, sooner or later, run out of screen space

Parallel co-ordinates Usable for up to 150

variates Unworkable greater than

250 variates

Remote sensing: (5 variates, 16,384 observations)

12

18 April 2007


Brushing as a Solution Brushing selects a

restricted range of one or more variables

Selection then highlighted

Note outlier

13

18 April 2007


Glyph Techniques – Star Plots

Each observation represented as a ‘star’

Each spike represents a variable

Length of spike indicates the value

14

18 April 2007


Glyph Techniques – Star Plots – Iris Data

Each observation represented as a ‘star’

Each spike represents a variable

Length of spike indicates the value

Iris data set

15

18 April 2007


Multivariate Visualization Techniques

Software: Xmdvtool

Matthew Ward Techniques designed for any number of variables

– Scatter plot matrices

– Parallel co-ordinates

– Glyph techniques

http://davis.wpi.edu/~xmdv

16

18 April 2007


Visualizing Structures of Information

17

18 April 2007


Examples of Networks of Information

My Window filestore

Automobile web site- visualizing links

18

18 April 2007


Suppose user hasthree subdirectories:A, B and C

First partition in Xaccording to totalsize of each sub-directory

A B C

Tree Map of Filestore

Note we are seeingthe relative sizesof directories

19

18 April 2007


A B C

Then within eachsubdirectory, wecan partition in Yby the size ofindividual files,or furthersubdirectories

Tree Map of Filestore

20

18 April 2007


Treemap Example

Usenet newsgroups

For history oftreemaps see:www.cs.umd.edu/hcil/treemap-history

Developed over many years by Ben Schneiderman and colleagues

21

18 April 2007


Tree Maps – A Filesystem

Download SequoiaView from:http://www.win.tue.nl/sequoiaview/-Developed by Jarke van Wijk andcolleagues

Can be hard to decipher so..

22

18 April 2007


Visualizing Structure of Web Pages Star trees have been successfully used to visualize web site

structures Place home page in centre

with linked pages connected by hyperbolic arcs further arcs link to further links

Escher woodcut… .. inspired:

23

18 April 2007


Star Trees

Automobilesweb site

Home pagein centre

Click on linkyou want ...

24

18 April 2007


Star Trees

Auto Historymoves to centre of screen

Click on nextlink... And so on

25

18 April 2007


Star Trees Commercially available from

Inxight Spun out of Xerox PARC www.inxight.com

26

18 April 2007


Visualizing Web Searches

www.kartoo.co.uk

27

18 April 2007


Interacting with Visualizations

28

18 April 2007


Interaction

Major difference between paper and computer-based visualization is ability to interact with picture and alter the presentation of the data

We have already seen brushing and here we look at the idea of focus and context

A recurring problem in visualization is lack of screen real estate

Want to achieve: Focus: to see detail of immediate interest Context: to see the overall picture

Want to do this interactively…

29

18 April 2007


Bifocal Display Magnify focus, demagnify

context A possible application is in

map reading This London underground

application was developed by Marcelo Cohen in Leeds

Zoom / pan Focus /context

30

18 April 2007


What is the Bifocal Display Doing? Transforming the information

space to the display space Visual transfer functions

Informationspace

DisplaySpace Normal

display

Informationspace

DisplaySpace

Bifocaldisplay

context

focus

31

18 April 2007


The Perspective Wall

2D layout wrappedaround a 3D structure

Space utilisation:-detail on centrepanel 3x size ofequivalent flat wall fitting field ofview

32

18 April 2007


Multiple Views Multiple views can also be used

to provide focus and context Powerpoint uses this to good

effect!

33

18 April 2007


Time Visualizations

34

18 April 2007


Visual Metaphors : Long time periods

Special techniques have been proposed for visualization over very long time periods

Themeriver technique has been used to depict evolutionary behaviour…

.. Possible with Excel

Evolution of baby names.... Try it at:http://babynamewizard.com/namevoyager/lnv0105.html

Laura and Martin Wattenberg

35

18 April 2007


Themeriver Themeriver for climate change… …

36

18 April 2007


River Metaphor Taglines

Visualizing tags attached to Flickr online image sharing

Evolution over time Show tags that are specific to a

time period

http://research.yahoo.com/taglines/

37

18 April 2007


Cluster and Calendar based Visualization of Time Series Data

Jarke van Wijk has shown how visualization can be used in analysis of time series data

Opposite is power demand within ECN (Netherlands Energy Research Centre)…

… hard to pick out patterns of usage

38

18 April 2007


Visualizing the Main Clusters By clustering the 365 days

into 6 clusters of similar behaviour, we are able to visualize the key patterns of use…

… but better still, in next slide we link to a calendar

39

18 April 2007


Calendar View of Power Demand

40

18 April 2007


Calendar View of Number of Employees at Work

http://www.win.tue.nl/~vanwijk/clv.pdfWhat can you observe? (NB Dec 5th)

41

18 April 2007


Spiral Graphs Spiral graphs are a space-

efficient way of visualizing long time series…

From Alexa et al

42

18 April 2007


Time Wheel The Time Wheel allows several

time series to be viewed simultaneously…

… how successful is this? … rotation can help, why? … again cf parallel coordinates?

Tominski, Abello, Schumann - Rostock

1 18 April 2007 vizNET-LEEDS-PRES-0002-070418 A Rough Guide to Data Visualization – Part 2 VizNET...

Documents

Transcript of 1 18 April 2007 vizNET-LEEDS-PRES-0002-070418 A Rough Guide to Data Visualization – Part 2 VizNET...