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Chapter 7

Clustering and Grouping

Analyzing Social Media Networks with NodeXLInsights from a Connected World

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FIGURE 7.1C

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A network of three densely connected clusters, each shown inside a dashed circle. Ties between clusters are rare and less dense.

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FIGURE 7.2C

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Unfiltered 2007 U.S. Senate co-voting network showing all 48 senators connected to each other. Other columns in the NodeXL Edges worksheet show the number of times each pair of senators voted the same and their percentage agreement. A weak tie (Akaka and Allard) and a strong tie (Akaka and Baucus) are highlighted. “Raw” visualizations like this require refinement to display useful insights.

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FIGURE 7.3C

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The NodeXL Autofill Columns window with Edge Visibility Options set to “Greater Than 0.65” and Edge Opacity Options set to a range of 0.65 (edge opacity 10) to “The largest number in the column” (edge opacity 100).

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FIGURE 7.4C

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The 2007 U.S. Senate co-voting network graph after using Autofill Columns (see Fig. 7.3), setting Vertex Shape to Label, and Edge Color to (128, 128, 192). The Fruchterman-Reingold Layout visually creates two clear groups with a few boundary spanners in the middle after enough iterations.

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FIGURE 7.5C

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NodeXL Layout Options window used to increase the repulsive force between vertices, helping spread out vertices to reduce overlap.

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FIGURE 7.6C

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The 2007 U.S. Senate co-voting network after applying the Find Clusters feature and choosing to view the Graph Element – Clusters from the NodeXL ribbon. Each of the three automatically identified clusters is given a name, color, and shape on the Clusters worksheet.

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FIGURE 7.7C

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The NodeXL Cluster Vertices worksheet that maps each vertex into exactly one cluster. For example, Collins is the only member of Cluster C14, whereas Specter, Smith, and the others are members of Cluster C143.

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FIGURE 7.8C

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The Cluster Vertices worksheet used to manually map each vertex (senators) to a cluster (political party).

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FIGURE 7.9C

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The NodeXL Clusters worksheet showing the four unique clusters and their associated colors and shapes: Democrats (D) in blue, Republicans (R) in red, and Independents (I) and Independent Democrats (ID) in dark orange.

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FIGURE 7.10C

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Les Misérables character co-appearance network with automatically identified clusters represented by unique color and shape combinations.

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FIGURE 7.11C

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Lobbying Coalition network connecting organizations (vertices) that have jointly filed comments on U.S. Federal Communications Commission policies (edges). Vertex size represents number of filings and color represents eigenvector centrality (pink higher). Darker edges connect organizations with many joint filings. Vertices were originally positioned using Fruchterman-Reingold and handpositioned to respect clusters identified by NodeXL’s Find Clusters algorithm.