Drawing Graphs using Dot and Graphviz
Table of Contents
tup]] : How I use Emacs Org Mode to write novels and short stories
1 License
Copyright (C) 2013, 2014 Tony Ballantyne. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
Code in this document is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This code is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
2 Introduction
2.1 What is DOT?
DOT is a plain text graph description language. It is a simple way of describing graphs that both humans and computer programs can read.
2.2 What is Graphviz?
Graphviz is open source graph visualization software. Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks.
2.3 Who is this document for?
This document was originally written as quick reference for myself. It was then extended to become a tutorial for Computing students. It's now offered to anyone who wants to learn DOT by example.
2.4 Related Materials
You can find links to similar documents posts at my blog TonyBallantyne.com/tech
If you have stumbled across this document by accident whilst looking for my work as an SF and Fantasy writer, the following links may be more useful to you
- TonyBallantyne.com: Blog about my novels and short stories
- Emacs Tutorial : A brief introduction to Emacs for writers
- My Emacs Writing Setup : How I use Emacs Org Mode to write novels and short stories
3 Setup
You will need to have the Graphviz suite of programs installed on your computer to follow this tutorial. Graphiz can be downloaded for free from the Graphviz site: http://www.graphviz.org/Home.php
4 Basic Examples
4.1 Simple Graph
graph graphname {
a -- b;
b -- c;
b -- d;
d -- a;
}
4.2 Same Graph, Different Layout
graph graphname {
rankdir=LR; //Rank Direction Left to Right
a -- b;
b -- c;
b -- d;
d -- a;
}
4.3 Simple Digraph (Directional Graph)
digraph graphname{
a -> b;
b -> c;
a -> c;
}
4.4 Simple Digraph with Labels
digraph graphname{
T [label="Teacher"] // node T
P [label="Pupil"] // node P
T->P [label="Instructions", fontcolor=darkgreen] // edge T->P
}
4.5 Same Graph, Different Shape and Colour
digraph graphname {
T [label="Teacher" color=Blue, fontcolor=Red, fontsize=24, shape=box] // node T
P [label="Pupil" color=Blue, fontcolor=Red, fontsize=24, shape=box] // node P
T->P [label="Instructions", fontcolor=darkgreen] // edge T->P
}
Here are some of the shapes you can use… box, polygon, ellipse, oval, circle, point, egg, triangle, plaintext, diamond, trapezium, parallelogram, house, pentagon, hexagon, septagon, octagon, doublecircle, doubleoctagon, tripleoctagon
There are lots more available here… http://www.graphviz.org/content/node-shapes
4.6 Summary
digraph summary{
start [label="Start with a Node"]
next [label="Choose your shape", shape=box]
warning [label="Don't go overboard", color=Blue, fontcolor=Red,fontsize=24,style=filled, fillcolor=green,shape=octagon]
end [label="Draw your graph!", shape=box, style=filled, fillcolor=yellow]
start->next
start->warning
next->end [label="Getting Better...", fontcolor=darkblue]
}
5 More Advanced
5.1 Saving Time
It takes time defining each node individually. The following way is quicker
digraph hierarchy {
nodesep=1.0 // increases the separation between nodes
node [color=Red,fontname=Courier,shape=box] //All nodes will this shape and colour
edge [color=Blue, style=dashed] //All the lines look like this
Headteacher->{Deputy1 Deputy2 BusinessManager}
Deputy1->{Teacher1 Teacher2}
BusinessManager->ITManager
{rank=same;ITManager Teacher1 Teacher2} // Put them on the same level
}
5.2 Records
You can now use HTML to define these sort of blocks. Find out more at http://www.graphviz.org/doc/info/shapes.html
digraph structs {
node[shape=record]
struct1 [label="<f0> left|<f1> mid dle|<f2> right"];
struct2 [label="{<f0> one|<f1> two
}" shape=Mrecord];
struct3 [label="hello
world |{ b |{c|<here> d|e}| f}| g | h"];
struct1:f1 -> struct2:f0;
struct1:f0 -> struct3:f1;
}
6 Some Example Graphs
6.1 Finite State Machine
digraph finite_state_machine {
rankdir=LR;
size="8,5"
node [shape = circle];
S0 -> S1 [ label = "Lift Nozzle" ]
S1 -> S0 [ label = "Replace Nozzle" ]
S1 -> S2 [ label = "Authorize Pump" ]
S2 -> S0 [ label = "Replace Nozzle" ]
S2 -> S3 [ label = "Pull Trigger" ]
S3 -> S2 [ label = "Release Trigger" ]
}
6.2 Data Flow Diagrams
digraph dfd{
node[shape=record]
store1 [label="<f0> left|<f1> Some data store"];
proc1 [label="{<f0> 1.0|<f1> Some process here
}" shape=Mrecord];
enti1 [label="Customer" shape=box];
store1:f1 -> proc1:f0;
enti1-> proc1:f0;
}
6.3 Data Flow Diagrams 2
The following uses subgraphs to display different levels. Note that subgraphs must start with the prefix cluster_ or they won't work. It will only work with dot layout.
digraph dfd2{
node[shape=record]
subgraph level0{
enti1 [label="Customer" shape=box];
enti2 [label="Manager" shape=box];
}
subgraph cluster_level1{
label ="Level 1";
proc1 [label="{<f0> 1.0|<f1> One process here
}" shape=Mrecord];
proc2 [label="{<f0> 2.0|<f1> Other process here
}" shape=Mrecord];
store1 [label="<f0> |<f1> Data store one"];
store2 [label="<f0> |<f1> Data store two"];
{rank=same; store1, store2}
}
enti1 -> proc1
enti2 -> proc2
store1 -> proc1
store2 -> proc2
proc1 -> store2
store2 -> proc1
}
6.4 Object Inheritance
digraph obj{
node[shape=record];
rankdir="BT";
teacher [label = "{<f0> Teacher|<f1>
|<f2>
}"];
course [label = "{<f0> Course|<f1>
|<f2>
}"];
student [label = "{<f0> Student|<f1>
|<f2>
}"];
lesson [label = "{<f0> Lesson |<f1>
|<f2>
}"];
tutorial [label = "{<f0> Tutorial|<f1>
|<f2>
}"];
assessment[label = "{<f0> Assessment|<f1>
|<f2>
}"];
coursework [label = "{<f0> Coursework|<f1>
|<f2>
}"];
exam [label = "{<f0> Exam|<f1>
|<f2>
}"];
{rank=same; teacher course student}
teacher->course [dir="forward",arrowhead="none",arrowtail="normal",headlabel="1",taillabel="1.."];
student->course [dir="forward",arrowhead="none",arrowtail="normal",headlabel="1",taillabel="1.."];
lesson->course [dir="forward",arrowhead="diamond",arrowtail="normal"];
tutorial->course [dir="forward",arrowhead="diamond",arrowtail="normal"];
assessment->course [dir="forward",arrowhead="diamond",arrowtail="normal"];
coursework->assessment;
exam->assessment;
}
6.5 Entity Relationship
digraph ER{
node[shape=box];
Book;
Customer;
Loan;
{rank=same;Book,Customer,Loan}
Book->Loan[dir="forward",arrowhead="crow",arrowtail="normal"];
Customer->Loan[dir="forward",arrowhead="crow",arrowtail="normal"];
}
7 Reference
Here are the most useful attributes you will need when drawing graphs. The full list can be found here: http://graphviz.org/doc/info/attrs.html
7.1 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
7.2 Vertex Attributes
- [label="Some Label"] Labels the Vertex
- [color="red"] Colors the Vertex
- [fillcolor="blue"] Fills the Vertex with the specified colour
7.3 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
7.4 Size, Background Colour
fixedsize=true; size="1,1"; resolution=72; bgcolor="#C6CFD532";
8 Appendices
8.1 Further Reading
8.2 Using Emacs Org Mode
Emacs org mode is an ideal environment for writing, executing and exporting Dot graphics
8.2.1 Setup
Download and install graphviz and add the path to the exec-path variable
You will need to update your .emacs file to load dot as a babel language. The following is a useful babel setup for dot and other languages
(org-babel-do-load-languages
(quote org-babel-load-languages)
(quote ((emacs-lisp . t)
(java . t)
(dot . t)
(ditaa . t)
(R . t)
(python . t)
(ruby . t)
(gnuplot . t)
(clojure . t)
(sh . t)
(ledger . t)
(org . t)
(plantuml . t)
(latex . t))))
8.2.2 Embedding Dot in Emacs
Org mode can interpret different languages by using the Library Of Babel. To do so, enclose the code in begin_ src and end_ src tags as below. You'll need to add command line arguments as shown.
A shortcut to make a begin_ src block is to type <s [TAB]
#+begin_src dot :file ./img/example1.png :cmdline -Kdot -Tpng
graph graphname {
a -- b;
b -- c;
b -- d;
d -- a;
}
#+end_src
8.2.3 The Command Line
The section :cmdline -Kdot -Tpng in the #+begin_ src dot :file ./img/example1.png :cmdline -Kdot -Tpng section are command line arguments. They tell dot how to render and display.
- -Kdot use dot layout. The other layouts you can try are Kneato, Kcirco, Ktwopi, Kfdp and Ksfdp for different layouts
- -Tpng render as png
The full command line arguments can be found here: http://graphviz.org/content/command-line-invocation