Information Visualization: Trees Chris North cs3724: HCI

Info Visualization Review Multi-dimensional data vis Navigation strategies

Trees (Hierarchies) What is a tree? DAG, one parent per node items (can have attributes) + structure Data structure: parent ptr, array of children, LM child+RS Size: #nodes = b height ResultSet -> Tree? categorical Parent ptr Path name

Examples Example trees: book libraries, folders, family trees, threaded msgs NCAA march madness!!!! Aisles, websites, org charts Tasks: search, drill down, browsings Structural analysis, parents, children, Least common ancestor

2 Approaches Connection node & link E.g. TreeView widget Containment node in node E.g. Venn diagram A CB A BC

Detail Only Dos: tree Whats the problem?

TreeView Widget Good for directed search tasks Good for text labeled nodes Not good for learning structure No attributes Apx 50 items visible Lose path to root for deep nodes Scroll bar! Error rate high Fitt’s Law? Too many small distant things

Mac Finder

Overview+Detail Maryland

Focus+Context Hyperbolic Tree (star tree) Radial; shrink with distance to center Drag to navigate Scalability? Xerox PARC, Inxight

Miniaturization Disk Tree Xerox PARC

3D ConeTrees Rotate subtrees Pro: Con: Xerox PARC

Ugh!

FSN SGI file system navigator Jurassic Park

2 Approaches Connection node & link E.g. TreeView widget Containment node in node E.g. Venn diagram A CB A BC

Zooming TreeMaps Slice and Dice, space filling Node size & color encodes data attribute Zoom on subtrees Good for fixed-height trees Scalability? Maryland

“Squarified” TreeMap

Cushion TreeMaps Free file directory browser Van Wijk Map of the Market

Radial Containment SunBurst Radial slicing Animated zooming Focus+Context Georgia Tech

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 scalability?

Multiple Foci? Focus on 2 distant regions simultaneously Microsoft Research