Hierarchy and Tree Visualization

Transcription

1 Hierarchy and Tree Visualization

2 Definition Hierarchies An ordering of groups in which larger groups encompass sets of smaller groups. Data repository in which cases are related to subcases

3 Hierarchical Data Family histories, ancestries File/directory systems on computers Organization charts Object-oriented software classes Queen Victoria s Family Tree

4 Hierarchy Visualization Allow adequate space within nodes to display information Allow users to understand relationship between a node and its context Allow to find elements quickly Fit into a bounded region

5 Trees Hierarchies are often represented as trees Two major categories of tree visualization techniques Node-link diagram Visible graphical edge from parents to their children Space-filling

6 Node-Link Diagrams Root at top, leaves at bottom is very common

7 Different Styles

8 Windows Explorer A very popular visualization

9 Decision Tree Manual decision tree

10 Organization Chart Obama administration

11 When there are lots of nodes Showing more attributes of data cases in hierarchy or focusing on particular applications of trees Interactive exploration

12 Space Tree

13 Why Put Root at Top or Left Root can be at center with levels growing outward too Any node might be the root From J. Stasko s slides

14 Radial View Tree Recursively position children of a subtree into circular wedges the central angle of these wedges are proportional to the number of leaves

15 Radial View Tree

16 Balloon View Tree Siblings of sub-trees are included in circles attached to the father node Melancon, G., Herman, I.: Circular drawing of rooted trees. Reports of the Centre for Mathematics and Computer Sciences (CWI), INSR9817

17 Balloon View Tree

18 3D Approaches

19 Botanical Tree

20 Pros Pros and Cons More effective area to lay out tree Use of smooth animation to help person track updates Aesthetically pleasing Cons 3D occlusion obscures some nodes Non-trivial to implement and requires some graphics horsepower

21 Collapsible Cylindrical Tree Basic idea: use a set of nested cylinders according to the telescope metaphor Limitation: one path is visible Interactions: rotation, go down/up Dachselt & Ebert Infovis 01

22 Hyperbolic Browser Find a space (hyperbolic space) that increases exponentially, lay the tree on it Transform from the hyperbolic space to 2D Euclidean space J. Lamping and R. Rao, The Hyperbolic Browser: A Focus + Context Technique for Visualizing Large Hierarchies, Journal of Visual Languages and Computing, vol. 7, no. 1, 1995, pp

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25 Hyperbolic Browser

26 Hyperbolic Browser R. Spence. Information Visualization

27 Hyperbolic Browser Change Focus R. Spence. Information Visualization

28 Key Features Natural magnification (fisheye) in center Layout depends only on 2-3 generations from current node Smooth animation for change in focus Don t draw objects when far enough from root (simplify rendering)

29 Space-Filling Techniques Each item occupies an area Children are contained within parent

30 Visualization of Hierarchical Data by Circle Packing Tree visualization using nested circles Brother nodes represented by externally tangent circles Nodes at different levels displayed by using 2D nested circles or 3D nested cylinders W.Wang et al. CHI 2006

31 Circle Packing Visualization of a file system

32 Example Visualizing a class hierarchy of software

33 Treemap Children are drawn inside their parents Alternative horizontal and vertical slicing at each successive level Use area and color to encode node attributes B. Johnson, Ben Shneiderman: Tree maps: A Space-Filling Approach to the Visualization of Hierarchical Information Structures. IEEE Visualization 1991:

34 Treemap Very popular visualization tool -source-flex-component-treemap-2-1-0/

35 Treemap Features It is rectangular! It makes better use of space Good representation of two attributes beyond node-link: color and area Not as good at representing structure Can get long-thin aspect ratios What happens if it s a perfectly balanced tree of items all the same size?

36 Aspect ratios J. Stasko s slides

37 Showing Structure A tree with 698 node (from [Balzer:infovis2005])

38 Showing Structure Borderless treemap: hard to discern structure of hierarchy What happens if it s a perfectly balanced tree of items all the same size? Variations Use border Change rectangles to other forms

39 Nested vs. Non-nested

40 Nested Treemap Borders help on small trees, but take up too much area on large, deep ones

41 Cushion Treemap Add shading and texture Van Wijk and Van de Wetering InfoVis 99

42 Voronoi Treemaps Enable subdivisions of and in polygons Fit into areas of arbitrary shape balzer:infovis05

43 Treemap Applications Software visualization Multimedia visualization Tennis matches File/directory structures Basketball statistics Stocks and portfolios

44 Marketmap

45 Internet News Groups the Usenet newsgroup discussion community space generated by the Netscan system at Microsoft Research

46 Photemesa Image browser

47 Major References Jing Yang, Lecture notes, UNCC Colin Ware. Information visualization, 2004 Daniel Keim. Tutorial note in InfoVis 2000 John Stasko. Course slides, Fall 2005