How to Improve the Appearance of Dense Graphs

Oct 27, 2008 at 4:26 PM
Edited Oct 27, 2008 at 4:33 PM

A coworker recently asked me how she might improve the appearance of a .NetMap graph that had so many edges it appeared to be a mass of black ink.  Here are the suggestions I made to her.

  • Change the opacity of some or all of the edges.  You can change the default edge opacity by clicking Options in the graph pane.  Change it to something smaller than the default value of 10 and all the edges will become translucent.  You can alter the opacity for individual edges by using the Opacity column on the Edges worksheet.
  • Experiment with edge colors.  Set a default edge color in Options, or use the Color column on the Edges worksheet for per-edge control.
  • Change the graph pane's background color.  You'll find this in Options.  A different background can often improve the graph's overall appearance.
  • Increase the size of the graph pane.  The edge widths and vertex radii stay constant as the graph pane grows, so a larger pane spaces things out and can improve legibility.  You can drag the graph pane out of Excel and resize it to fill your entire screen.  (Getting it docked again is a bit finicky, though.)
  • Lay out the graph repeatedly.  Clicking "Lay Out Again" in the graph pane often improves the layout when using the default Fruchterman-Reingold layout type.
  • Try different layouts.  Use "Layout Type" in the graph pane to select a different layout, then click "Lay Out Again."
  • Filter the edges.  If every edge doesn't need to be shown, try filtering them.  The Visibility column on the Edges worksheet controls which edges actually get shown.  You can fill in the column manually, or plug in an Excel formula that determines visibility based on values in other columns.  You can also use the .NetMap, Graph, AutoFill Columns ribbon command to do this automatically.  Or you can use the Dynamic Filter feature added to version 1.0.1.58, which gives you a set of sliders to hide edges and vertices in real time based on numeric columns in the workbook.
  • Try clustering, which automatically assigns the same color and shape to groups of related vertices.  Hover over the .NetMap, Analysis, Create Clusters ribbon command for details on this.  Clustering affects the appearance of vertices, not edges, but it's another technique for helping to clarify opaque graphs.

-- Tony