Visualization Layouts¶

Graph drawing or network diagram is a pictorial representation of the vertices and edges of a graph. This drawing should not be confused with the graph itself, very different layouts can correspond to the same graph. In the abstract, all that matters is which pairs of vertices are connected by edges. In the concrete, however, the arrangement of these vertices and edges within a drawing affects its understandability, usability, fabrication cost, and aesthetics.

The problem gets worse, if the graph changes over time by adding and deleting edges (dynamic graph drawing) and the goal is to preserve the user’s mental map.

Conventions¶

Graphs are frequently drawn as node-link diagrams in which the vertices are represented as disks, boxes, or textual labels and the edges are represented as line segments, polylines, or curves in the Euclidean plane.

Node-link diagrams can be traced back to the 13th century work of Ramon Llull, who drew diagrams of this type for complete graphs in order to analyze all pairwise combinations among sets of metaphysical concepts.

Alternative conventions to node-link diagrams include:

Adjacency representations such as circle packings, in which vertices are represented by disjoint regions in the plane and edges are represented by adjacencies between regions.

Intersection representations in which vertices are represented by non- disjoint geometric objects and edges are represented by their intersections.

Visibility representations in which vertices are represented by regions in the plane and edges are represented by regions that have an unobstructed line of sight to each other.

Confluent drawings, in which edges are represented as smooth curves within mathematical train tracks.

Fabrics, in which nodes are represented as horizontal lines and edges as vertical lines.

Visualizations of the adjacency matrix of the graph.