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Information VisualizationInformation Visualization

Ji Y

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Jing YangSpring 2010

Hierarchy and Tree Visualization

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Hierarchies

DefinitionA d i f i hi h lAn ordering of groups in which larger groups encompass sets of smaller groups.

Data repository in which cases are related to subcases

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Hierarchies in the WorldFamily histories, ancestriesFile/directory systems onFile/directory systems on computersOrganization chartsObject-oriented software classes

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Good Hierarchy Visualization

Allow adequate space within nodes to display informationinformationAllow users to understand relationship between a node and its contextAllow to find elements quicklyFit into a bounded regionMuch more

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Much more

Trees

Hierarchies are often represented as treesDi t d li hDirected, acyclic graph

Two major categories of tree visualization techniques:

Node-link diagram Visible graphical edge from parents to their children

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childrenSpace-filling

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Node Link DiagramsNode-Link Diagrams

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Node-Link Diagrams

Root at top, leaves at bottom is very common

8J. Stasko’s InfoVis class slides

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Different Styles

Rectangular: Well suited for displaying labeled/scaled trees.

Straight: Works well only on rooted binary trees.

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Smooth Edges: Very similar to the rectangular mode

Radial: Works well for visualizing unrooted trees.

http://www.hyphy.org/docs/GUIExamples/treepanel.html

Microsoft Explorer

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Decision Tree

11http://bigpicture.typepad.com/writing/2008/04/decision-tree.html

www.answers.com/topic/decision-tree

Organization Chart

12Edraw Organizational Charts: an organization chart drawing software

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When there are lots of nodes…

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Position children “below” their common ancestors

Layout can be top-down, left-to-right and grid like positioning

Fast: linear time

E. Reingold and J. Tilford. Tidier drawing of trees. IEEE Trans. Softw. Eng., SE-7(2):223-- 228, 1981

The Challenges

Scalability# f d i ti ll# of nodes increases exponentially Available space increases polynomially (circular case)

Showing more attributes of data cases in hierarchy or focusing on particular applications of trees

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applications of treesInteractive exploration

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Space Tree

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http://www.cs.umd.edu/hcil/spacetree/

Video

Why Put Root at Top (Left)

Root can be at center with levels growing outward tooCan any node be the root?

16J. Stasko’s InfoVis class slides

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Radial View

Recursively position children of a subchildren of a sub-tree into circular wedgesthe central angle of these wedges are proportional to the

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proportional to the number of leaves

P. Eades, “Drawing Free Trees”, Bulleting of the Institutefro Combinatorics and its Applications, 1992, pp. 10-36.

Radial View

18Infovis contest 03 Treemap, Radial Tree, and 3D Tree Visualizations

Nihar et. al. Indiana University

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Balloon View

Siblings of sub-trees are included in circles attached to the father nodeattached to the father node.

19Melancon, G., Herman, I.: Circular drawing of rooted trees. Reports ofthe Centre for Mathematics and Computer Sciences (CWI), INSR9817,

Balloon View

20Melancon, G., Herman, I.: Circular drawing of rooted trees. Reports ofthe Centre for Mathematics and Computer Sciences (CWI), INSR9817,

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3D Tree

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Tavanti and Lind, InfoVis 01

Cone Tree

Key ideas:Add thi d di i i t hi h l tAdd a third dimension into which layout can goCompromise of top-down and centered techniques mentioned earlierChildren of a node are laid out in a cylinder “below” the parentSiblings live in one of the 2D planes

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Siblings live in one of the 2D planes

Robertson, Mackinlay, Card CHI ‘91

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Cone Tree

23Robertson, Mackinlay, Card CHI ‘91

Alternative Views

24Robertson, Mackinlay, Card CHI ‘91

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Advantages vs. Limitations

PositiveMore effective area to

NegativeAs in all 3D occlusionMore effective area to

lay out treeUse of smooth animation to help person track updatesAesthetically pleasing

As in all 3D, occlusion obscures some nodesNon-trivial to implement and requires some graphics horsepower

25J. Stasko’s InfoVis class slides

Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Basic idea: we can easily see the branches, leaves and their arrangement in a botanicalleaves, and their arrangement in a botanical treeInspiration: Strand model of Holton

Strands: internal vascular structure of a botanical tree

26Node and link diagram Corresponding strand Model

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Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Use strand model to create a 3-d directory tree:tree:

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Unsatisfied features: 1. Branching points 2. long and thin branches 3. cluttered leaves

Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Adding smooth transition between two cylinders

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Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Use a general tree rather than a binary tree

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Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Phi-ball with one (left) and many (right) files

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Phi-ball with one (left) and many (right) files

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Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Botanical tree:

31Final model with the improvements

Botanical Tree [E. Kleiberg et. al. InfoVis 2001]

Botanical tree:

32The same directory with different settings

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Collapsible Cylindrical Tree [Dachselt & Ebert Infovis 01]

Basic idea: use a set of nested cylinders according to the telescope metaphoraccording to the telescope metaphorLimitation: one path is visible in onceInteractions: rotation, go down/up

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Collapsible Cylindrical Tree [R. Dachselt, J. Ebert Infovis 01]

Example application: web document browsing

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Hyperbolic Browser

Key idea: Fi d (h b li ) th t iFind a space (hyperbolic space) that increases exponentially, lay the tree on itTransform from the hyperbolic space to 2D Euclidean space

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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. 33-55.

36http://graphics.stanford.edu/~munzner/talks/calgary02

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Hyperbolic Browser

39R. Spence. Information Visualization

Change Focus

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Key Attributes

Natural magnification (fisheye) in centerL t d d l 2 3 ti fLayout depends only on 2-3 generations from current nodeSmooth animation for change in focusDon’t draw objects when far enough from root (simplify rendering)

41J. Stasko’s InfoVis class slides

H3 Browser

Use hyperbolic transformation in 3D space

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Demo

Tamara Munzner: H3: laying out large directed graphs in 3D hyperbolic space. INFOVIS 1997: 2-10

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Space Filling TechniquesSpace-Filling Techniques

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Space-Filling Techniques

Each item occupies an areaChild “ t i d” ithi tChildren are “contained” within parent

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Visualization of Large Hierarchical Data by Circle Packing W.Wang et al. CHI 2006

Key ideas: t i li ti i t d i ltree visualization using nested circlesbrother nodes represented by externally tangent circlesnodes at different levels displayed by using 2D nested circles or 3D nested cylinders

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Visualization of Large Hierarchical Data by Circle Packing W.Wang et al. CHI 2006

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Visualization of Large Hierarchical Data by Circle Packing W.Wang et al. CHI 2006

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Visualization of Large Hierarchical Data by Circle Packing W.Wang et al. CHI 2006

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Treemap

Children are drawn inside their parentsAlt ti h i t l d ti l li i tAlternative horizontal and vertical slicing at each successive levelUse area and color to encode node attributes

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B. Johnson, Ben Shneiderman: Tree maps: A Space-Filling Approach to the Visualization of Hierarchical Information Structures. IEEE Visualization 1991: 284-291

Treemap

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http://www.juiceanalytics.com/writing/10-lessons-treemap-design/

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Treemap Affordances

It is rectangular! It makes better use of spaceG d t ti f t tt ib t b dGood representation of two attributes beyond node-link: color and areaNot as good at representing structure

Can get long-thin aspect ratiosWhat happens if it’s a perfectly balanced tree

f it ll th i ?

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of items all the same size?

Aspect ratios

52J. Stasko’s InfoVis class slides

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Treemap Variation

Make rectangles more square

Slice-and-dice Cluster Squarified

53Pivot-by-middle Pivot-by-size Strip

Showing Structure

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A tree with 698 node (from [Balzer:infovis2005]

How about a perfectly balanced binary tree?

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Showing Structure

Borderless treemap: hard to discern structure of hierarchyof hierarchy

What happens if it’s a perfectly balanced tree of items all the same size?

Variations:Use borderCh t l t th f

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Change rectangles to other forms

Nested vs. Non-nested

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Non-nested Treemap Nested Treemap

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Nested Treemap

Borders help onBorders help on small trees, but take up too much area on large, deep ones

57http://www.cs.umd.edu/hcil/treemap-history/treemap97.shtml

Cushion Treemap

Add shading and texture (Van Wijk and Van de Wetering InfoVis’99)de Wetering InfoVis 99)

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Voronoi Treemaps [balzer:infovis05]

Enable subdivisions of and in polygonsFit i t f bit hFit into areas of arbitrary shape

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Treemap Applications

Software visualizationM lti di i li tiMultimedia visualizationTennis matchesFile/directory structuresBasketball statisticsStocks and portfolios

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p

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Marketmap

61http://www.smartmoney.com/marketmap/

Software Visualization

SeeSys (Baker & Eick, AT&T Bell Labs)

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New code in this release

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Internet News Groups

Netscan (Fiore & Smith Microsoft)

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SequoiaView

File visualizater www.win.tue.nl/sequoiaview/

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PhotemesaImage browser (quantum and bubble treemap) http://www.cs.umd.edu/hcil/photomesa/p p

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Space-Filling Techniques

Each item occupies an areaChild “ t i d” ithi ( d ) tChildren are “contained” within (under) parent

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One Example

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Icicle Plot

Icicle plot (similar to Kleiner and Hartigan’s concept of castles)concept of castles)

Node size is proportional to node width

67Barlow and Neville InfoVis 2001

Radial Space Filing Techniques

InterRing [Yang02]

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Node Link + Space Filling Techniques

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Elastic Hierarchies: Combining Treemaps and Node-Link Diagrams [zhao:infovis 05]

A hybrid approachD iDynamic

Video

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Space-Optimized Tree [Q. Nguyen and M. Huang Infovis 02]

Key idea:Partition display space into a collection of geometricalPartition display space into a collection of geometrical areas for all nodesUse node-link diagrams to show relational structure

71Example: Tree with approximately 55000 nodes

Example: Tree with 150 nodes