Tutorial

Natalia Andrienko and Gennady Andrienko

 
 
 

Fraunhofer AIS – Institute for Autonomous Intelligent Systems Schloss Birlinghoven, Sankt-Augustin, D-53754 Germany http://www.ais.fraunhofer.de/and e-mail: {Natalia.Andrienko, Gennady.Andrienko}@ais.fraunhofer.de

 

Abstract

The importance of exploratory data analysis (EDA) as a prerequisite to application of computational methods, such as traditional statistical analysis, is currently widely recognised. The goal of EDA is to gain understanding of data, i.e. to penetrate into relationships, patterns, and trends hidden inside data and to formulate hypotheses that can later be checked using statistical methods. Preliminary investigation of data must also precede their preparation to processing by various computation-based analysis tools, such as data mining.

Techniques of EDA are mostly based on data visualisation, i.e. the graphical presentation of data in ways that prompt the discovery of important traits and relationships. Computers enabled features of graphical presentations that are now considered indispensable for EDA: high user interactivity, allowance for various transformations, and multiple dynamically linked views such that changes in one display are immediately propagated to all others. An important category of data dealt with in statistics is spatially referenced data. For visualization of such data, maps are traditionally used, since they are isomorphic to space and thus capable of representing and conveying to human’s eye significant spatial relationships. High degree of user interactivity is a general requirement to map displays intended to support “spatial thinking”, i.e. hypothesis generation, data analysis, and decision making. Examples of possible user interactions include:

• Dynamic linking of maps with other types of graphical displays by so-called “brushing”: objects selected in one of the displays are simultaneously highlighted in all of them;
• tools for changing in real time parameters of conventional cartographic methods such as the classes in a choropleth map;
• various interactive devices for controlling map animation

Still, interactive techniques and tools can support information exploration and knowledge construction only when users are able to properly utilise these instruments. User studies demonstrate that effective use of the novel techniques requires learning of the new concepts and ideas. Users are able to understand and adopt the new ideas concerning map interactivity and manipulability. However, these ideas needed to be appropriately introduced; people could not grasp them just from the appearance of the maps and controls.

The general topic of the proposed tutorial is visualisation of spatial data as a tool for exploratory data analysis, problem solving, and decision-making. The tutorial will be based on the CommonGIS system developed by the SPADE team. The system is available for free use for research and educational purposes. The participants will receive CD-ROMs containing fully functional CommonGIS system and a variety of demonstration projects.

Most of the tools considered in the tutorial are unique for CommonGIS since this system have been specially designed for the most efficient support of EDA and decision-making. However, the experience gained in the tutorial can be also utilised in work with commercially available software. In many cases, operations that are effectively “packed” in CommonGIS into a single tool may be done in other packages through sequences of data transformation, calculation, and visualization operations. Some recommendations concerning data exploration and decision making with the use of available commercial software will be given.

The tutorial will be held in 1,5 hours and consists of a lecture combined with demonstration. Depending on the availability of equipment, the participants can be given an opportunity for the individual work with the demonstrated tools. For better organisation of the tutorial, it is desirable to supply participants with computers, at least 1 PC per 2 participants. The use of private laptops is also possible.
 

Expected audience

1. People who are performing analysis of spatially- and temporally-related data as a part of their professional activities;
2. Decision makers who are interested in making informed decisions;
3. Researchers interested in novel techniques of interactive graphical data analysis.

Tutorial structure

1. Introduction to EDA. Cartographical visualisation of spatially referenced data. Major techniques for thematic mapping. Interactive vs. traditional (static) maps.
2. Interactive map manipulation techniques for visual data analysis:
1. choropleth maps with tools for focusing, visual comparison, and pattern investigation;
2. dynamic classification  and cross-classification maps;
3. bar charts and pie charts with tools for visual comparison and focusing.
3. Dynamic linking of maps and other graphical displays
1. simultaneous highlighting of corresponding objects;
2. dynamic query;
3. propagation of classes.
4. Data analysis in space and time
1. map animation; analytical interactive tools for animated maps;
2. time plots and their transformations;
3. space-time cube.
5. Decision making
1. different styles of multiple criteria decision making;
2. ideal point method;
3. dynamic utility symbols;
4. generalised Pareto set, combination with dynamic query

Illustrations: some interactive maps and plots

Figure 1. Screenshot of usage of dynamically linked displays in a problem-solving session

Figure 2. Effect of outlier removal (focusing). Due to a very high value of the birth rate in Albania all other countries in the map on the left seem to be coloured almost uniformly. When Albania is taken out of consideration (“removed”), differences between the other countries can be represented more distinctly. The operation is performed using interactive focussing control; see its appearance left and right to the map for initial and final states.

Figure 3. Visual comparison technique. On the left, the birth rate in Germany is chosen as the reference value. Countries with higher values are painted in shades of brown, and countries with lower values in shades of blue. On the right, the reference value has been changed to equal the birth rate in France. In CommonGIS this is actually achieved just by a mouse click on France. Alternatively, user can click on a colour band (shown left and right to the map) to set the reference value.
 

Instructors:

Appendix I Survey of CommonGIS history and functionality

Apendix II Selected publications