GraphViz Examples and Tutorial

Reference

Graphs and Vertices (Called Nodes in the GraphViz notation) may have a large number of attributes that affect both the graph's actual layout, and details like colours, labels, and line types. I cover a few of the attributes below but for a full reference see the GraphViz Attribute Index

Attributes

Graph Attributes

label="My Graph";Label a graph itself
rankdir=LR;Lay the graph out from Left to Right, instead of Top to Bottom
{rank=same; a, b, c }Group nodes together at the same level of a graph
splines="line";Force edges to be straight, no curves or angles
K=0.6;Used to influence the 'spring' used in the layout, Can be used to push nodes further apart, which is especially useful for twopi and sfdp layouts

Vertex Attributes

[label="Some Label"]Labels the Vertex
[color="red"]Colors the Vertex
[fillcolor="blue"]Fills the Vertex with the specified colour

Edge Attributes

[label="Some Label"]Labels the Edge (Useful for Weights)
[color="red"]Colors the Vertex (Useful for Paths)
[penwidth=2.0]Adjusts the thickness of the edge line, Very useful for Paths

Edges may also have a weight attribute, defined as [weight=0.5] for example, but note that this doesn't display the weight directly, It instead acts as a hint to the graph layout to give this edge a more direct routing.

Graphs

Graphs are defined as either a graph or a digraph using fairly standard syntax, similar to an edge list.

 graph {
                node1 -- node2;
                node3 -- node2;
                }

 digraph {
                node1 -> node2;
                node3 -> node2;
                }

Vertices

Vertices are defined with a simple plaintext label,

A, B, C, Test, Vertice1,
            some_vertex

, etc. If you need a more complicated label you can declare the vertex first, before defining an edge, and give it a label attribute, for example:

 digraph {
                someVertex[label="A Complicated Label"];
                someVertex -> node2;
                node2 -> node3;
                }

Edges

For the most part the only concern with edges is their colour/thickness, and Label, as the rest is handled automatically by the graph/digraph definition, To color an edge apply the color attribute to the graph definition as follows

 digraph {
                node1 -> node2[color="red"];
                }

To Display a weight, we give the vertex itself a label, similar to how we label nodes

 digraph {
                node1 -> node2[label="0.2"];
                node2 -> node3[label="0.2"];
                }

We can actually apply any label we like to edge in this way

 digraph {
                node1 -> node2[label="edge1"];
                node2 -> node3[label="edge2"];
                }

You may combine these attributes in any way you please

 digraph {
                node1[label="Some Complicated Label"];
                node1 -> node2[label="An Edge",color=red];
                node2 -> node3;
                }

GraphViz Pocket Reference