Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Overview of Data Visualization

Avatar for Martin Smith Martin Smith
November 04, 2008
77

Overview of Data Visualization

Avatar for Martin Smith

Martin Smith

November 04, 2008
Tweet

Transcript

  1. Visualization? • Practically any technique using images or diagrams for

    communication • Not new – cartography is old • Not old – computer graphics are young • Wide applications: architecture, product design, education, communication • A Periodic Table of Visualization Methods
  2. From social structure, to data, to visualization • People &

    relationships as data • Mathematical graphs as social networks • Network analysis as applied graph theory
  3. Graph theory – Graph drawing • Leonhard Euler, functions, f(x),

    e, i, Σ, and Seven Bridges of Königsberg, Prussia
  4. Graph layout • Hierarchical – source to sink • Tree

    – roots without cycles • Symmetric – create visual symmetry • Orthogonal – min. area & edge crossing • Spectral – eigenvectors of a matrix • Force/MDS – springs and electric charges
  5. Evaluating graph drawings • Is it fast to compute? Can

    we parallelize it? • Does the algorithm converge? How quickly? • Does it show obvious symmetries? • Can we adapt it with parameters? • Does it minimize edge crossings? • Does vertex nearness reflect adjacency? • Are sizes, distances and shapes distributed uniformly? • Election 2008 visualization – let’s evaluate
  6. Fleming, Lee, and Adam Juda. "A Network of Invention." Harvard

    Business Review 82, no. 4 (April 2004).
  7. Force-directed algorithms • Attractive and repulsive forces simulated as a

    physical system • Forces can be gravity (Newton), springs (Hooke), charged particles (Coulomb), magnetism (Maxwell?) • Advantages: quality, flexibility, interactivity • Disadvantages: can be slow, hurt by local minima or initial conditions
  8. Two common force-directed algorithms • Fruchterman-Reingold: Nodes as steel rings,

    edges as springs, electrical repulsive force, step width using a global cooling temperature definition • Kamada-Kawai: Same as above, but instead of a temperature, minimize force equations with some initial node criteria
  9. High school dating: Data drawn from Peter S. Bearman, James

    Moody, and Katherine Stovel, Chains of affection: The structure of adolescent romantic and sexual networks, American Journal of Sociology 110, 44-91 (2004).
  10. What can we do to make graph drawing better for

    social networks? • Modify the graph, improve data collection • Add constraints to force-directed algorithm • Get better initial conditions, more iterations • Deal with orientations and coordinate systems • 3D -> 2D, or use more interesting forces • Apply multiple layout algorithms • Curved lines and uniform distributions
  11. EgoNet (egonet.sf.net) • Java, Swing – hosted at SourceForge •

    Java Universal Network/Graph Framework • Currently defaults to F-R, but places isolates regularly instead of randomly • We’d like to explore other optimizations
  12. Thank you! • survey.bebr.ufl.edu/hsa6930/ - ‘other’ • Martin Smith -

    martins@bebr.ufl.edu • EgoNet: http://egonet.sf.net/ • JUNG: http://jung.sourceforge.net/
  13. References • 1. Freeman, L., Visualizing Social Networks. Journal of

    Social Structure 1(1), Carnegie-Mellon, 2000. • 2. Giuseppe Di Battista, Peter Eades, Roberto Tamassia, Ioannis G. Tollis. Algorithms for Drawing Graphs: an Annotated Bibliography. Computational Geometry: Theory and Applications 4:235-282, 1994. • 3. Tamassia, R. Advances in the Theory and Practice of Graph Drawing. Theoretical Computer Science 217 (2), 1999. • 4. Fruchterman, T. M. J., & Reingold, E. M. Graph Drawing by Force- Directed Placement. Software: Practice and Experience, 21(11), 1991. • 5. Kamada, T. & Kawai, S. (1989). An algorithm for drawing general undirected graphs. Information Processing Letters, 31, 7-15. • 6. Network Workbench Community Wiki at https://nwb.slis.indiana.edu/community/?n=VisualizeData.HomePage