Readability Metrics for Network
Visualization
Cody Dunne and Ben Shneiderman
Human-Computer Interaction Lab &
Department of Computer Science
University of Maryland
Contact: cdunne@cs.umd.edu
26th Annual Human-Computer Interaction Lab Symposium
May 28-29, 2009 College Park, MD
Citations between papers in the ACL Anthology Network
NetViz Nirvana
1. Every node is visible
2. Every node’s degree is countable
3. Every edge can be followed from source to
destination
4. Clusters and outliers are identifiable
Readability Metrics
• How understandable is the network drawing?
• Continuous scale [0,1]
• Example: Journal may recommend
– 0% node occlusion
– <2% edge tunneling
– <5% edge crossing
• Also called aesthetic metrics
• Global metrics are not sufficient to guide users
• Node and edge readability metrics
Specific RMs
• Node Occlusion
– Proportional to number
of distinguishable items
– 1: Each node is uniquely
distinguishable
– 0: All nodes overlap in
connected mass
C
B
A
D
Specific RMs (cont)
• Edge Crossing
– Number of crossings
scaled by approximate
upper bound
A
C
B
D
Specific RMs (cont)
• Edge Tunnels
• Number of tunnels scaled by
approximate upper bound
• Local Edge Tunnels
• Triggered Edge Tunnels
C
A
B
D
SocialAction
•
•
•
•
•
Social network analysis tool
Statistical measures
Attribute ranking
Multiple coordinated views
Papers:
–
–
–
A. Perer and B. Shneiderman
Balancing Systematic and Flexible Exploration of Social Networks
IEEE Transactions on Visualization and Computer Graphics, 2006, 12, 693-700
A. Perer and B. Shneiderman
Integrating statistics and visualization: case studies of gaining clarity during exploratory data analysis
CHI '08: Proceeding of the 26th annual SIGCHI Conference on Human Factors in Computing Systems,
ACM, 2008, 265-274
A. Perer and B. Shneiderman
Systematic yet flexible discovery: guiding domain experts through exploratory data analysis
IUI '08: Proc. 13th International Conference on Intelligent User Interfaces, ACM, 2008, 109-118
Contributions
•
•
•
•
Global readability metrics
Node and edge readability metrics
Real-time RM feedback as nodes are moved
Integrated into attribute ranking system
Demo
Rank by:
Node Occlusion
Node occlusion: 14
Edge tunnels:
70
Edge crossings: 180
Spring coeff: 9 x10 5
Rank by:
Node Occlusion
Node occl:
4(-10)
Edge tunnel: 26(-44)
Edge cross: 159(-21)
Spring coeff: 9 x10 6
Rank by:
Node Occlusion
Node occl:
0(-4)
Edge tunnel: 14(-12)
Edge cross: 157(-2)
Spring coeff: 9 x10 7
Rank by:
Local Edge Tunnel
Node occl:
0(-0)
Edge tunnel: 14(-0)
Edge cross: 157(-0)
Spring coeff: 9 x10 7
Rank by:
Local Edge Tunnel
Node occl:
0 (-0)
Edge tunnel: 0(-14)
Edge cross: 155(-2)
Spring coeff: 9 x10 7
Rank by:
Edge Crossing
Node occl:
0(-0)
Edge tunnel:
0(-0)
Edge cross: 155(-0)
Spr. coeff: 9 x10 7
Rank by:
Edge Crossing
Node occl:
0(-0)
Edge tunnel:
0(-0)
Edge cross: 85(-70)
Spr. coeff: 9 x10 7
Future Work
• Snap-to-Grid tool pulls node to local maxima
• Feedback for layout algorithms
• Evaluation
– NetViz Nirvana useful for teaching network analysis
• E. M. Bonsignore, C. Dunne, D. Rotman, M. Smith, T. Capone, D. L. Hansen and B.
Shneiderman
First Steps to NetViz Nirvana: Evaluating Social Network Analysis with NodeXL
Submitted, 2009
– Integration into NodeXL to test RM effectiveness
• www.codeplex.com/nodexl
• M. Smith, B. Shneiderman, N. Milic-Frayling, E. M. Rodrigues, V. Barash, C. Dunne, T.
Capone, A. Perer and E. Gleave
Analyzing (Social Media) Networks with NodeXL
C&T '09: Proc. Fourth international conference on Communities and Technologies,
Springer, 2009
Conclusion
• Global RMs to judge readability of network
drawings
• Node and Edge RMs for interactive
identification of problem areas
• Network analysts and designers of tools
should take drawing readability into account
Paper
C. Dunne and B. Shneiderman
Improving Graph Drawing Readability by
Incorporating Readability Metrics: A Software
Tool for Network Analysts
HCIL Tech Report HCIL-2009-13, Submitted, 2009
Contact
cdunne@cs.umd.edu
Additional RMs
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•
•
•
Angular Resolution
Edge Crossing Angle
Node Size
Node Label
Distinctiveness
• Text Legibility
• Node Color & Shape
Variance
• Orthogonality
• Spatial Layout &
Grouping
• Symmetry
• Edge Bends
• Path Continuity
• Geometric-path
Tendency
• Path Branches
• Edge Length
Layout:
Force-Directed Layout
Contrasts in meaning between thesaurus categories
Interactions between graph-summarized groups proteins
within the human body
Collaboration between cancer research organizations
Node occlusion:
Edge tunnels:
Edge crossings:
?
?
?
Rank by:
Local Edge Tunnel
Node occlusion: 23
Edge tunnels:
383
Edge crossings: 2104
Rank by:
Local Edge Tunnel
Node occlusion:
0
Edge tunnels:
154
Edge crossings: 2032