Getting started with Graphviz.
Diagrams with Emacs, graphviz and org-babel.

1 Configuration

First, Install graphviz using (on Ubuntu 11.10)

sudo apt-get install graphviz

Next, Download planetUML from http://plantuml.sourceforge.net/download.html Save the .jar file into your favourite apps directory, e.g. ~/apps

Finally, setup .emacs file using the instructions given here.

2 Hello World

Enter the following into an org-mode buffer and then publish (C-c C-e)

#+begin_src dot :file helloworld.png :cmdline -Kdot -Tpng
digraph test123 {
   a [label="hello"];
   b [label="world"];
   a -> b;
}
#+end_src

Should generate a file helloworld.png that looks like this:

example1.png

3 Nodes - shapes, labels and colours

There are a number of pre-defined shapes - box, circle, rectangle, etc. To change a node shape, simple enter shape="type" in the node [attribute] list, so for example:

#+begin_src dot :file helloworld.png :cmdline -Kdot -Tpng
digraph test123 {
   config [label="config", shape="tab"];
   source [label="source", shape="folder"];
   jekyll [label="Jekyll", shape="oval"];
   site [label="site", shape="folder"];
   config -> jekyll;
   source -> jekyll;
   jekyll -> site;
}
#+end_src

Which will produce this:

example2.png

Other useful attributes include style=filled fillcolor=value (Red, Yellow,..)

4 Arrows and Connectors

The type of edges in a graph are set by the graph type - directed (digraph) graphs have edges that have arrows, and undirected (graph) have edges that do not have arrows.

The examples shown above are both digraph - directed graphs - so have arrows by default on the edges (which are defined in the source with ->). Undirected graphs have edges that are defined in source with – instead of ->

By default, directed graphs have edges with arrow-heads on the 'right' side of the edge.

There are a number of different arrow types that can be defined by by using the arrowhead and arrowtail attributes along with the dir attribute.

dir = 'forward' | 'back' | 'both' | 'none'

For example, the following code:

#+Begin_src dot :file ../media/dia/example3.png :cmdline -Kdot -Tpng
digraph example3 {
   candidate [label="Candidate", shape="rectangle"];
   reviewer [label="Reviewer", shape="rectangle"];
   appraisal [label="Appraisal", shape="rectangle"];
   report [label="Report", shape="rectangle"];
   candidate -> reviewer [label="invites", arrowhead="crow"]
   candidate -> appraisal [label="performs", dir="both", arrowhead="crow", arrowtail="crow"]
   appraisal -> report [label="generates", arrowhead="none"]
}
#+end_src

Produces the following diagram:

example3.png

Author: Stuart

Created: 2016-07-10 Sun 17:32

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