Information Visualization CMSC 838B Spring 2003 Trees

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Information VisualizationCMSC 838B Spring
2003Trees

• Benjamin B. Bederson
• University of Maryland
• www.cs.umd.edu/bederson

This presentation adapted from John Stasko
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Hierarchies (Trees)

• Definition
• Data repository in which cases are related to
  subcases
• Pervasive
• Family histories, ancestries
• File/directory systems on computers
• Organization charts
• Animal kingdom Phylum,, genus,
• Object-oriented software classes
• ...

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Trees

• Two main representation schemes
• Node-link
• Space-filling
• Approaches to scale
• Complex representation
• Navigation
• Elide (dont show) some nodes
• Show nodes at different sizes

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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

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Node-Link Diagrams

• Root at top, leaves at bottom is very common

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Why Put Root at Top?
Root can be at center with levels growing
outward too
Can any node be the root?
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Examples
Good for? Bad for?
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Drawing a Tree
How does one draw this?
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Space-Filling Representation
Each item occupies an area Children are
contained under parent
One example
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SunBurst Stasko et. al.
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Treemap Shneiderman et. al.
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Squarified
Slice-and-dice
Cluster
Pivot-by-middle
Strip
Pivot-by-size
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Variation Cushion Treemap
Add shading and texture to help convey
structure of hierarchy
Van Wijk 99
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Questions

• What tasks are best supported by each vis?
• Can multidimensional data per node be portrayed?
• How does the visualization scale?
• Can users quickly understand the representation?