DATA VISUALIZATION. Lecture 1 Introduction. Lin Lu llu@sdu.edu.cn

Transcription

1 DATA VISUALIZATION Lecture 1 Introduction Lin Lu llu@sdu.edu.cn

2 Visualization 可视化 Visualization now seen as key part of modern computing High performance computing generates vast quantities of data... High resolution measurement technology likewise... microscopes, scanners, satellites Information systems involve not only large data sets but also complex connections we need to harness our visual senses to help us understand the data... that is, to Data Visualization

3 Getting Started What is Visualization? - a definition Where is it useful? - some applications What is the history? What tools are now available? How are we going to study it?

5 First : An Experiment You need a watch with a second-hand Without using pencil and paper (or a calculator!!), multiply 72 by 34 How long did it take? Now you need pencil and paper as well as watch Multiply 47 by 54 How long did it take? Conclusion?

6 What is Visualization? Generally: Visualization is the use of computer-supported, interactive, visual representations of data to amplify cognition Data visualization is the study of the visual representation of data. The Goal of data visualization is to communicate information clearly and effectively through graphical means. Data visualization is related to Information Visualization and Scientific Visualization 可视化是利用计算机图形学和图像处理技术, 将数据转换成图形或图像在屏幕上显示出来, 并进行交互处理的理论方法和技术数据可视化主要旨在借助于图形化手段, 清晰有效地传达与沟通信息数据可视化这条术语实现了成熟的科学可视化领域与较年轻的信息可视化领域的统一

7 Visualization Twin Subjects Scientific Visualization Visualization of physical data Information Visualization Visualization of abstract data Ozone layer around earth Automobile web site - visualizing links

8 Visualization Bridging the Gap between the Computer and the Mind Human Information Analyst Visualization Computation Resources Information Resources

9 Scientific Visualization - What is it? Reality Observation Simulation Data Visualization Images, animation

10 Information Visualization Information Visualization Has emerged over last decade Building on success of scientific visualization Driven by the escalating volumes of data fuelled by the new technologies (eg supermarket checkouts!) and the accessibility of data via the Internet Characterised by large quantities of data not necessarily numbers and search for relationships amongst the data but no absolute dividing line between SciVis and InfoVis

11 学科分类图

13 Applications - Meteorology Pressure at levels in atmosphere - illustrated by contour lines in a slice plane Generated by the Vis5D system from University of Wisconsin (now Vis5d+) Vis5d: Vis5d+ :

14 Applications - Medicine From scanner data, we can visualize 3D pictures of human anatomy, using volume rendering Generated by Anatomy.TV used by our medical students to learn anatomy Look under Anatomy.TV in Library electronic resources

15 Applications Climate Prediction Simulation of 21 st century climate evolution Real-time display of results temperature, cloud, precipitation, etc Massive ensemble of runs : distributed public-resource computing project see to participate!

16 Applications Computational Fluid Dynamics Interface between immiscible fluids e.g. oil / water Loops and fingers arise when mixing starts Rayleigh-Taylor instability Simulated on ASCII Blue Pacific (Cook & Dimotakis, 2001) Interface visualized using a density isosurface

17 Applications Computational Fluid Dynamics Flow of air around a car Vectors and particle paths illustrate flow Coloured slice indicates pressure

18 Applications Integrative Biology in e-science project on Integrative Biology This involves modelling behaviour of human heart, and of cancer tumours Visualization is of electrical activity in heart, showing the spiral wave pattern that is a precursor to fibrillation

19 Applications - Astronomy The Astrogrid project is building a virtual observatory Visualization is a fundamental tool in presenting star maps and in understanding relationships between observations

20 Applications Information Networks Visualization can be applied to networks of information Chaomei Chen s Pathfinder visualizations have been used to study trends in scientific research Here we see articles on terrorism, coloured by year of publication, and clustered by topic For more on this, see:

22 Visualization BC Imagination or visualization, and in particular the use of diagrams, has a crucial part to play in scientific investigation. Who said this? When? There are many examples of the use of visualization Before Computers (BC) graph plots in 10th century business graphics in 18th century (Playfair) contour plots in 18th century (Halley) Answer: Rene Descartes, 1637

23 The First Visualization This and following two pictures are taken from Brian Collins Data Visualization - Has it all been seen before? in Animation and Scientific Visualization, Academic Press

24 The First Business Graphics

25 The First Contour Map

26 Visual Thinkers Many of the great scientists were good at visual thinking: Leonardo da Vinci James Clerk Maxwell Michael Faraday Albert Einstein This was often at the expense of verbal skills Tom West : In the Mind s Eye See also Maxwell s clay model now in New Cavendish Laboratory, Cambridge (picture by Tom West)

28 Early Computer Visualization From early days of computing, scientists have carried out numerical simulation - and looked to visualization to help understand the results. Visualization systems have evolved in four different styles - all still in use today (so not really history!)

29 Subprogram Libraries 1960 onwards Libraries of subprograms to draw graphs, contour plots Scientists include calls to library routines from within their own code Leading examples from era were: GHOST (UKAEA Culham) NAG Graphics Library NAG Graphics :

30 Subprogram Libraries This style continues today NAG Graphics Library still available vtk C++ classes provide modern version of this style Great flexibility but need to program Application Programming Interface vtk :

31 Interactive Packages From late 1970 onwards Specialist packages allowing data to be visualized using special purpose scripting language gnuplot Example: gnuplot Less flexible, but simpler (provided commands are easy to learn!)

32 Interactive Packages Matlab is a powerful system for computation and visualization Has its own C-like language

33 Interactive Packages This style continues today R is a powerful interactive environment for statistical computation and visualization Freely available for both linux and Windows

34 Interactive Packages The popularity of spreadsheets has brought a requirement to provide visualization charts Excel has a chart wizard to guide construction of a variety of chart types

35 Scientific Visualization Recent surge of interest in scientific visualization was sparked by an NSF report: Visualization in Scientific Computing McCormick, de Fanti and Brown Argued that investment in high performance computing in US was wasted unless there was corresponding investment in visualization This motivated a third style of visualization system...

36 Visual Programming Systems From late 1980s onwards Scientific visualization seen as a sequence of simple processing steps: eg contouring read in data create contour lines draw contour lines Systems provide modules implementing simple steps in a visualization pipeline Scientist uses visual programming to connect modules together

37 Visual Programming - IRIS Explorer

38 Visual Programming Systems Visual programming allows easy experimentation which is what one needs in visualization Examples are: IRIS Explorer AVS OpenDX (grown from IBM Visualization Data Explorer)

39 Service-based Visualization The Internet era has introduced a fourth style of system where a visualization service is delivered over the internet using Web technologies Client-side with Java applets.

40 Service-based Visualization or server side Here a form on a web page is used to make a visualization request Processed by a visualization system on server and returned to client as VRML the Web standard for 3D graphics

41 Service-based Visualization Kartoo allows you to visualize results of web searches.. See: Search for Envisioning Information

42 The Four Phases of Visualization Systems These four phases correlate with four phases in computing generally Subprogram libraries begun in era of batch computing Interactive packages begun in era of interactive computing, with terminals connected to host Visual programming systems begun in era of workstation computing, with graphical user interfaces Service-based visualization begun in era of internet computing

44 Module Outline - Lectures Introduction and historical view Fundamental concepts Scientific visualization Scalar values 1D, 2D, 3D Flow visualization Data tables multivariate data visualization Graphs and Networks Documents; maps; software Perception issues

45 Reference Material There is no single course textbook The Web is of course a fundamental resource Information Visualization Perceptual for Design Colin Ware (2004) Envisioning Information Edward Tufte Information Visualization R. Spence Addison-Wesley (2001) The Visualization Toolkit (3rd edition) W Shroeder, K Martin, W Lorensen Kitware Inc

46 Sources Wherever possible you should attempt to use high quality sources such as the following IEEE VIS (VAST, InfoVis, SciVis) ACM SIGGRAPH ACM SIGCHI IEEE Transaction on Visualization and Computer Graphics IEEE Computer Graphics and Applications

47 Objectives To be aware of the value of visualization to gain insight into both numeric data (from science, engineering and medicine for example) and also non-numeric information (such as networks and documents) To understand the fundamental techniques for data visualization To appreciate design issues in visualization To be skilled in the use of a number of state of art visualization systems