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Hierarchies (Trees)

Explore the concept of hierarchies and various tree visualizations, including node-link diagrams, treemaps, sunbursts, and more. Learn about the challenges in representing complex hierarchies and discover potential solutions.

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Hierarchies (Trees)

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  1. Hierarchies (Trees) • Definition • Data repository in which cases are related to subcases • Examples • Family histories, ancestries • File/directory systems on computers • Organization charts • Animal kingdom: Phylum,…, genus,… • Object-oriented software classes • ... Shengdong Zhao @ UofT

  2. Shengdong Zhao @ UofT

  3. 2 Main Approaches • Connection (node & link) • outliner • Containment (node in node) • Venn diagram A B C A B C Shengdong Zhao @ UofT

  4. Tasks • Help understand node characteristics or tree structure? • Some kinds of tasks: • Find a node • Revisit node • List node ancestors • Understand local topology • Understand global topology • Different Trees are good for different tasks Shengdong Zhao @ UofT

  5. Why is tree visualization hard? Structure AND items (Structure harder, consumes more space) Scaling: data size grows very quickly (exponential) #nodes = bheight How to provide Context (when focus changes) May be multiple hierarchies May be multiple focuses Shengdong Zhao @ UofT

  6. Current Status • Many 2D and 3D hierarchy visualizations • Each works for some tasks and some scales • Very few have had user testing Shengdong Zhao @ UofT

  7. Node-Link Diagrams Shengdong Zhao @ UofT

  8. Tree Shengdong Zhao @ UofT

  9. Distortion: Graphical Fisheye - 1992 • Sarkar & Brown, DEC SRC, CHI’92 Shengdong Zhao @ UofT

  10. Overview + Detail: PDQ Trees • Overview+Detail of 2D tree layout • Dynamic Queries on each level for pruning Shengdong Zhao @ UofT

  11. PDQ Trees Shengdong Zhao @ UofT

  12. Auto-arrangement + Thumbnail: Spacetree Shengdong Zhao @ UofT

  13. Different Orientation & Refocus: Hyperbolic Trees • Rao, “Hyperbolic Tree” • http://startree.inxight.com/ • Xerox PARC • Inxight • Focus+context Shengdong Zhao @ UofT

  14. Space Optimized TreeQuang & Mao (InfoVis 2002) Shengdong Zhao @ UofT

  15. 3D: Cone Trees • Robertson, “ConeTrees” • Xerox PARC • 3D for focus+context Shengdong Zhao @ UofT

  16. Space-Filling Representation Each item occupies an area Children are “contained” under parent One example Shengdong Zhao @ UofT

  17. Treemaps • Shneiderman, “Treemaps” • Vishal, Jeevak • http://www.cs.umd.edu/hcil/treemap3/ • Maryland Shengdong Zhao @ UofT

  18. Variation: Cushion Treemap Add shading and texture to help convey structure of hierarchy Van Wijk ‘99 Shengdong Zhao @ UofT

  19. Sunburst • Stasko, GaTech • Radial layout • Animated zooming Shengdong Zhao @ UofT

  20. Sunburst vs. Treemap • + Faster learning time: like pie chart • + Details outward, instead of inward • + Focus+context zooming • - Not space filling • - More space used by non-leaves • All leaves on 1-D space, perimeter • Treemap: 2-D space for leaves • - Smaller scale? Shengdong Zhao @ UofT

  21. CHEOPS • Beaudoin, “Cheops” • Jon, Mudita • http://www.crim.ca/hci/cheops/index1.html Shengdong Zhao @ UofT

  22. Challenges • Multiple foci • George Robertson, Microsoft Research Shengdong Zhao @ UofT

  23. Time Tube - 1998 • Chi et al., Xerox PARC, CHI’98 Shengdong Zhao @ UofT

  24. Taxonomy Visualization - 2000 • Graham et al., Napier Univ. IJHCS 2000 Shengdong Zhao @ UofT

  25. MultiTrees - 1994 • Furnas & Zacks, Bell Core, CHI’94 • DAG’s with shared subtrees Shengdong Zhao @ UofT

  26. Polyarchies • multiple inter-twined trees • Visual pivot • George Robertson, Microsoft Research Shengdong Zhao @ UofT

  27. Research Questions • Can multidimensional data per node be portrayed? • How does the visualization scale? • What tasks are best supported by each vis? • Can users quickly understand the representation? Shengdong Zhao @ UofT

  28. Observations • It’s hard to preserve the structure of the tree and allow scalability • Different approaches are good for certain tasks with certain scale, and one single approach often has limitations and can’t solve a range of problems well • Change of representations require learning • Possible Solution • Try a hybrid approach to balance the structure and scalability • Create a solution with continuous variations for a range of tasks • Use animation to help users to understand the representation Shengdong Zhao @ UofT

  29. Node Link vs. Space Filling • Advantage of Node Link • Show Structure and Item • Natural • Disadvantage: • Hard to scale (100 nodes) • Advantage of Space Filling • Using 100% of screen space, scalable • monitoring and detect patterns in leaf nodes • Disadvantage: • Harder to see the structure Shengdong Zhao @ UofT

  30. What about combining the two techniques to create a continuous series of smooth representations and use animation to help users to understand the these representations better Shengdong Zhao @ UofT

  31. Several Ideas • Create animated transition between linked tree and treemaps Shengdong Zhao @ UofT

  32. Intermediates Shengdong Zhao @ UofT

  33. Overview + Detail Shengdong Zhao @ UofT

  34. Questions • Is this a worthwhile research topic? • Suggestions for further directions? • Any other combinations? • Which variation of the hybrid model is good for what tasks? (Scale?) • Anything else? Shengdong Zhao @ UofT

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