How to Draw Graphs: Seeing and Redrafting Large Networks in Security and Biology

Abstract

A graph is a mathematical object consisting of a set of vertices and a set of edges connecting vertices. Graphs can be drawn on paper in various ways, but until recently all published methods of drawing graphs have had undesirable properties: (i) for graphs which are not plane embeddable, intersections between the lines representing edges appear at points which are not vertices, creating the appearance of vertices where none exist, (ii) vertex labels can be placed inside vertex symbols, but there is no consistent, logical, and visually clean place to put edge labels, and (iii) representations of large graphs are visually dense and difficult to interpret. This paper describes a new cartographic method of drawing graphs which solves all of these problems, and has other advantages as well. Complements, comparisons and contrasts of graphs are usually better shown cartographically than in node-link form.