Overview
What is a network?
A visualization centered on pairwise interactions:
- A flight network
- A network of cooperative interactions between dolphins
- A network of aggressive interactions between fish
- A network of proteins and biochemical pathways
- A hierarchical diagram of relationships
Interactors are generally indicated by nodes, and interactions by edges
How are these interactions characterized?
- Weighted networks have different importance to the edges
- In directional networks, edges have direction
- In multipartite networks, nodes are divided into two types that interact only with each other
- Multimodal networks show different types of links
What are we trying to show?
- Relationships between particular nodes
- Patterns of clustering
- Paths and distances (six degrees of separation)
- Relationship between network structure and other variables
Aesthetics
Layout
- May reflect the network structure
- Usually by using force-directed algorithms (hairball)
- Or hierarchical clustering (dendrogram)
- Or something else about the data
- most often physical location
- Or a logical pattern
- or categories (hive plot)
Other node aesthetics
- Size can be used for importance (should have a scaleable, physical interpretation)
- Can be good for things about role in the network (e.g. betweenness, centrality)
- Color can be used for quantitative or qualitative attributes
- Choose a color scale that reflects this role
- Shape can be used for qualitative attributes
- It is possible to be creative about shape; e.g., use png icons
Edge aesthetics
Strongly constrained; they’re basically lines, and the nodes are drawn first
Use width to indicate edge “weight” (nothing else)
Use color to indicate edge type for a multi-modal graph
Use arrows to indicate direction on a directional graph
- Curvature can be used to show edges more clearly
- Rarely, to carry information
Labelling
Principles
- Don’t drop weights without a good reason
- consider carefully how weights are scaled
- Similarly for dropping specific edges
Size matters
- Level of detail and messages will change a lot depending on how many nodes you have
- Very big networks may show only the pattern of node clustering
- If you have many nodes, but only a few important ones, it may be possible to follow the above edge principles
- Rescale node size to improve visualization
- Communicate clearly about rescaling
Layout matters
Resources
Resources
Sites
Examples
