Graphics Reference
In-Depth Information
frame of reference, making it easier to spot change. Applying the layout to
all of the nodes ensures that space is reserved for each node to appear.
The product affinity data example already spans the full date range, making
it easy to apply layout across time. When data instead describes the graph
separatelyateachpointintime,youmustcomputeanaggregatedgraphthat
includes all nodes and links. Assign nodes their maximum size over time to
reserve space for them to reach their full scale.
Returning to the graph in Gephi, turn off the date range filtering, and apply
the Force Atlas 2 layout with overlap prevention on until the graph resolves
itself, and then turn it off. Re-apply the date range filtering to restrict the
visible graph to the first quarter of the time range. Export the resulting
image for comparison, and then repeat the same process for the other three
quarters.
Note
As of this writing, Gephi does not have a good method for viewing
multiple graph snapshots at once. To experiment with viewing
snapshots side by side, paste the images into a presentation tool like
PowerPoint.
Figure 15-3
illustrates the result of viewing multiple snapshots in time using
a fixed layout. The three Tufte topics that appear in each of the four views
provide consistent markers that anchor each view, and clearly when nodes
do not move, changes are more easily understood. Unlike the previous
example, here it is apparent that the cluster that seemed to disperse in fact
disappeared, while new nodes appeared nearby.
To be able to see change at the node level more clearly, even more labels
have been filtered out, leaving only those that are referenced most often. At
a high level, the story told here (albeit with a very small sample of data) is of
interestfirstbythedesigncommunityappearinginthesecondtimeinterval,
then by statisticians in the third interval, and by software architects in the
final interval.
