Graphics Reference
In-Depth Information
Figure 4-9:
The http://internet-map.net shows a map of 350,000
websites, organized by a force-directed layout.
Copyright 2014 by Ruslan Enikeev (used with permission)
Some care should be taken with this approach. It is feasible for nodes that
are not actually close to each other to be close in a force-directed graph,
particularly with sparse graphs and only gravity pushing nodes apart. In
fact, a graph with no links, but some gravity to pull nodes together and some
repulsion to keep some spacing between nodes, can create a nice-looking,
but meaningless, layout.
Time Oriented
Somekindsofgraphshavenodesorganizedbytime.Patentshavereferences
to earlier examples—each reference is a directed edge. Tracking down
successive references generates a directed graph. Consider an example.
A client involved in a patent investigation was excited at the prospect of
visualizing the relationship between patents. A typical force-directed layout
results in a visualization that clearly shows clustering such as
Figure 4-10
,
which was created with Cytoscape using the Prefuse layout. However, there
is no sense of time—two nodes beside each other may have occurred at
completely different times.
