For this tutorial, download and open this tulip graph file. This graph represent relations between authors, conferences and papers in the InfoVis community.
To distinguish between paper, conferences and authors, let us color them:
Select all papers: click
Edit → Find or Ctrl+F, set property: "type", set the filter "= 0".
Color the nodes in red: click
Graph Editor → Property,
select the 'viewColor' property, check
selected only, click
Set all and choose red.
Let's look at a single author, for instance George Robertson.. Select that node with the Find tool, with "titleshort" "=" "G.*Rob.*" (this is a regular expression). Temporarily moving the node away gives a rough estimate of how connected he is:
Now, focus on the graph around this author:
Algorithm → Selection → Reachable Sub-Graph, leaving direction to 0 (outgoing edges), startingNodes to viewSelection (nodes selected, in our case simply Mr. Robertson), and distance 1.
Edit → Create Subgraphto save this selection for further manipulation, naming it "GR.1hop.outgoing". Select this new subgraph in the hierarchy tab. We can deselect the nodes now: use selection tool and click away from any node or edge (or Ctrl+Shift+a).
Algorithm → Size → Auto Sizing, then change the layout for
Algorithm → Layout → Hierarchical → Hierarchical Graph. There is an even better hierarchical layout on the plugin server:
Help → Plugins → LaBRI Universite Bordeaux 1 → Layout → Sugiyama (OGDF).
We see which papers were published first, as they are cited by the later ones.
Robertson has 11 papers referenced in this database.
If we apply a coloring by the number of citations (
Algorithm → Color → Metric Mapping, with field property set to "arityOut" )
we clearly see that "Cone Trees" is his most influential work:
Algorithm → Selection → Reachable Sub-Graphalgorithm again, but with a depth of 2 to find all papers that cite a paper written by Robertson.
Edit → Invert Selectionor Ctrl + I), delete (Del). This leaves us with Robertson and all his papers, and the papers citing his papers.
You can now close this graph since we use another one for the next part. The next graph is similar to the this one but, has coauthorship edges linking authors who write papers together. Download it and open it.
Here we focus on the relationship between two authors, in this case Robertson and Card.
Edit → Find, check option
add, enter the regexp ".*Card.*".
Algorithm → Selection → Reachable Sub-Graphwith distance 1. We get the graph of all publications and coauthors of Card and/or Robertson.
One can repeat those operations for Robertson only and Card only:
The similarity of these final three images shows the very strong ties between these two authors.
You can now close this graph. The next graph is similar to the old one, but the links are from author to papers, and from papers to conferences. Download it here and open it in tulip.We used the following to show the large-scale structure of this dataset:
Algorithm → Selection → Induced subgraph, Create subgraph.
Algorithm → Layout → Force Directed → GEM)
Here is a close-up:
To select only the giant connected component (the largest connected set nodes),
select a node in the center of the giant component and run
Algorithm → Selection → Reachable Subgraph
with distance 1000 and directed=2.
Algorithm → Measure → Graph → Eccentricity, with "Closeness centrality" checked.
To get a approximation of top conferences, we can look for the ones where the number of authors is high.
To do so, click
Algorithm → Measure → Graph → Degree :
Algorithm → Measure → Graph → Strahler to see strong ties between conferences and authors:
Algorithm → General → Convolution,
the value of the discretization parameter should be near 30 to obtain 5 clusters:
One gets the following clusters:
The Strahler-Convolution clustering yields five clusters, according to increasing centrality. The first cluster is mostly yellow, and contains most of the data. The second cluster contains a next tier of 26 authors that have had a relatively strong impact. The third cluster contains a group of 7 influential authors (Chi, Bederson, Eick, Rao, Pirolli, Ward, and Brown), and the fourth cluster (Roth, Robertson, Keim, and Stasko) is yet more central. The fifth cluster is the single node of Mackinlay, and the last one is Card and Shneiderman. Our automatic clustering method clearly yields plausible results in this case.
In the last section, we use this graph.
To see the metanode labels,
View editor → Layers Manager, check
The clusters have been computed using
Algorithm → General → Strength.
The overview image from the previous section, showing the graph of all authors and papers, is extremely cluttered.
The previous section showed one way to extract information (find the most important nodes by convolution clustering).
Another clustering approach, small-world clustering, allows instead to navigate through a hierarchical subdivision of the entire dataset.
The simplified overview allows to understand the graph's high level structure.
The strength metric computes the number of cycles of length 3 and 4 passing through each edge, normalized by the maximum possible value.
The first image shows the clustered dataset.
Small-world navigation is useful when exploring an unfamiliar graph to quickly find the structure of complex components.
The eccentricity metric (
Algorithm → Measure → Graph → Eccentricity),
which measures whether nodes are peripheral (here in yellow) or central (here in blue), guides us to complexity immediately.
This metric is O(n^3), but the small-world decomposition simplifies the graph, making the computation tractable.
Here is a close-up of the node that has many blue lines leading to it:
We then open that cluster (right-click on the metanode,
go inside), which is itself a small-world graph:
We once again zoom towards the most central node with many blue edges, where we see a cluster containing the InfoVis 96 conference and all the authors who only published at the infovis community in that year.
We see this star shaped small-world decomposition only for the InfoVis conferences, because of the nature of this dataset: only the InfoVis conferences have a complete set of authors and papers available.