SNA 2.1

Getting Started with NodeXL, Layout, Visual Design, and Labeling

Purpose: NodeXL is an open-source extension for Microsoft Excel designed to make Social Network Analysis (SNA) and visualization accessible to non-programmers.
Structure: It uses a structured workbook template with multiple worksheets:
- Edges: Stores the “edge list” (pairs of connected vertices).
- Vertices: Stores information about individual nodes (color, size, shape, etc.).
- Clusters/Groups: Information about subsets of the network.
Scale: Typically supports networks of several thousand vertices (up to tens of thousands for some users).

Requirements: Windows Excel 2007 or 2010. (Not compatible with Mac Excel or older Windows versions).
Source: Downloadable from the Codeplex site (www.codeplex.com/NodeXL).
Opening: Access via the Start Menu or as an Excel Template (NodeXLGraph.xlsx).

Data Entry: You can manually type “Vertex 1” and “Vertex 2” names to create relationships.
Show Graph: Clicking “Show Graph” renders the data in the Graph Pane.
Highlighting: Clicking a row in the spreadsheet highlights the corresponding edge/vertex in the graph.
Importing: Data can be imported from:
- Existing files (Pajek, UCINET, GraphML).
- Social Media (Twitter, YouTube, Email collections).
- Copy-pasting from other Excel sheets.

Automatic Layouts:
- Fruchterman-Reingold: The default “force-directed” layout.
- Circle: Arranges nodes in a circle; useful for reducing edge crossings in small networks.
- Sugiyama / Harel-Koren: Other advanced algorithms for specific patterns.
Graph Types:
- Undirected: Symmetric relationships (e.g., “Friends”).
- Directed: Origin to destination (e.g., “Invitations”). Represented by arrows.
Manual Control:
- Manual Layout: Dragging nodes with the mouse to emphasize specific structures.
- Fixing/Locking: Vertices can be “Locked” via the Vertices worksheet (X and Y coordinates) to prevent them from moving during a refresh.
Navigation: Use the Zoom slider for detail and the Scale slider to adjust the size of all elements simultaneously.

Vertex Colors: Controlled by the “Color” column in the Vertices worksheet (uses standard CSS names like “Pink” or “Blue”).
Descriptive (Attribute) Data: Users can add custom columns (e.g., Age, Prior Party Attendance) to the right of the Vertices worksheet.
Autofill Columns: A powerful tool to map data to visual properties automatically.
- Example: Mapping “Number of Prior Parties” to “Vertex Size.”
Options Dialog: Allows setting the range (e.g., setting Min size to 2.1.5 and Max to 6.0) to prevent overlap or invisibility.
Legend: Automatically generated when using Autofill to help interpret the graph’s visual coding.

Vertex Labels:

2.1. Label as Shape: The text is the vertex; color and size apply to the text box.
1. Label alongside Shape: Text appears next to a shape (e.g., a Disk).
2. Tooltip: Text only appears when hovering over the node with a mouse.
Label Customization:
- Label Fill Color: Sets the background of the text box.
- Label Position: Can be set (Top, Bottom, etc.) to reduce clutter.
Images as Vertices: You can use image URLs or file paths in the “Image File” column to replace dots with profile pictures.
Edge Labels: Added via the “Label” column in the Edges worksheet to describe the relationship (e.g., “Phone call” vs. “Email”).

NodeXL’s primary advantage is its integration with the spreadsheet paradigm, making it easy for business analysts to use familiar formulas and filtering while generating professional network visualizations.
The Autofill feature is the bridge between raw data and meaningful visual patterns.

NetViz Nirvana: The research goal of reaching an ideal state where every node is visible, every degree is countable, and every edge can be followed.
Current Research Focus:
- User performance on benchmark tasks (e.g., “How fast can a user find a cluster?”).
- Automating layout while maintaining readability.
- Developing task-specific aesthetics for directed vs. undirected graphs.