Graphics Reference
In-Depth Information
In some software, you must wait for the iterations to finish before you
can click and drag nodes. In this case, you can still adjust the nodes and
then run the algorithm again (but make sure that the algorithm does not
reset all the positions each time you run it in the settings).
•
Label Adjust and other tweaking layouts
—There may also be
some additional layouts that are intended to be run after a
force-directed layout. The Label Adjust layout minimally pushes nodes
around to minimize the overlap of labels. Similarly, the Noverlap layout
pushes nodes around to minimize overlapping nodes.
•
Mix-and-match layouts
—Because the layouts are iterative, you can
also start with one layout and a little bit of another layout. In this mode
of experimenting with different layouts, it can be useful to slow down
the layout algorithms—each one has a speed setting (or a
step size
)
that can be reduced. The e-mail graph shown in the introduction to Part
2 (Figure P2-1) started with a Force Atlas 2 layout and then has some
Fruchterman Reingold added.
Tip
Some force-directed layouts can be different every time. There is
usually no way of going backward in force simulations, and sometimes
there is no undo. So, if you have a layout you like, save it.
Node-Only Layout
Sometimes you have so many links that it's not worth showing all of them.
Using a force-directed layout implies that the distance between adjacent
nodes indicates the strength of the connection between those nodes. For
large graphs, thousands or millions of links clutter the view, making it
impossible to see patterns. Instead, the links can be removed from the
display and the clusters and adjacencies are still visible.
For example, the
http://internet-map.net
by Ruslan Enikeev shown in
Figure 4-9
includes 350,000 websites with many millions of links. By
showing only the nodes, the viewer can see relative clustering and implied
relationships.
