Drawing Graphs using Dot and Graphviz

Drawing Graphs using Dot and Graphviz

Table of Contents

1. License

2. Introduction

2.1. What is DOT?

2.2. What is Graphviz?

2.3. Who is this document for?

2.4. Related Materials

3. Setup

4. Basic Examples

4.1. Simple Graph

4.2. Same Graph, Different Layout

4.3. Simple Digraph (Directional Graph)

4.4. Simple Digraph with Labels

4.5. Same Graph, Different Shape and Colour

4.6. Summary

5. More Advanced

5.1. Saving Time

5.2. Records

6. Some Example Graphs

6.1. Finite State Machine

6.2. Data Flow Diagrams

6.3. Data Flow Diagrams 2

6.4. Object Inheritance

6.5. Entity Relationship

7. Reference

7.1. Graph Attributes

7.2. Vertex Attributes

7.3. Edge Attributes

7.4. Size, Background Colour

8. Appendices

8.1. Further Reading

8.2. Using Emacs Org Mode

8.2.1. Setup

8.2.2. Embedding Dot in Emacs

8.2.3. The Command Line

tup]] : How I use Emacs Org Mode to write novels and short stories

1 License

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\n\n\n}" shape=Mrecord];
struct3 [label="hello\nworld |{ 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\n\n\n}" 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\n\n\n}" shape=Mrecord];
proc2 [label="{<f0> 2.0|<f1> Other process here\n\n\n}" 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> \n  |<f2> \n   }"];
course [label = "{<f0> Course|<f1> \n  |<f2> \n   }"];
student [label = "{<f0> Student|<f1> \n  |<f2> \n   }"];
lesson [label = "{<f0> Lesson |<f1> \n  |<f2> \n   }"];
tutorial [label = "{<f0> Tutorial|<f1> \n  |<f2> \n   }"];
assessment[label = "{<f0> Assessment|<f1> \n  |<f2> \n   }"];
coursework [label = "{<f0> Coursework|<f1> \n  |<f2> \n   }"];
exam [label = "{<f0> Exam|<f1> \n  |<f2> \n   }"];

{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

http://linuxdevcenter.com/pub/a/linux/2004/05/06/graphviz_dot.html

http://graphs.grevian.org/index.html

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

Date: <2013-10-21 Mon>

Author: Tony Ballantyne

Created: 2014-04-12 Sat 10:13

Emacs 23.3.1 (Org mode 8.0.2)

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