#+title: TLDR org mode + graphviz
#+date: <2019-05-21 19:50>

Org mode is pretty cool. Directed graphs are pretty cool. Let's see how they go together.

* Org mode
After installing the graphviz package, you will have the =dot= command. If you use it in with an org
mode source block like so:

#+BEGIN_SRC org
#+BEGIN_SRC dot :file ./dot-example.png  :cmdline -Kdot -Tpng
digraph {
    a -> b
}
,#+END_SRC
#+END_SRC

You can eval the block with =C-c C-c= and then view it inline in emacs by using
=org-toggle-inline-images=.

These blocks also export! Just like in [[https://github.com/neeasade/neeasade.github.io/blob/source/posts/2019-05-21-tldr-org-mode-%2B-graphviz.org#org-mode][this page itself!]]

#+BEGIN_SRC dot :file ./assets/posts/dot-example.png  :cmdline -Kdot -Tpng
digraph {
    a -> b
}
#+END_SRC

#+RESULTS:
[[file:./assets/posts/dot-example.png]]

* The Dot language

The dot language spec can be found [[https://www.graphviz.org/doc/info/lang.html][here]]. I don't
find that too helpful on it's own, so here are some notes:

Primitives that matter:

- a =node= is a bubble/self contained item that will be connected.
- an =edge= is the line that connect nodes.
- a =graph= is a the relation as a whole.

A list of attributes that can be applied to these can be found here: https://www.graphviz.org/doc/info/attrs.html

Some nice node options can be seen here: https://www.graphviz.org/doc/info/shapes.html#polygon

Here is an example that shows how attributes are set and some defaults I like:


#+BEGIN_SRC org
#+BEGIN_SRC dot :file ./dot-example.png  :cmdline -Kdot -Tpng
digraph {
    // config:
    // TBLR, top bottom left right, the direction of the graph.
    graph [rankdir=TB];
    // you can have multiple attrs per statement
    graph [dpi=150 splines=ortho];
    edge[decorate=true];
    node [shape=box];

    // definitions:
    // nb: setting definitions on their own is useful in larger graphs
    computer [label=computer];
    // quotes are optional, I'm using them when there are spaces
    phone [label="android phone"];
    router [label=router];

    // record syntax: | for horizontal, {|} for vert
    internet [shape=record label="{internet|cat pictures}"]

    // relations:
    computer -> router;
    phone -> router [label="wifi"];
    router -> internet [dir=both];
}
,#+END_SRC
#+END_SRC


#+BEGIN_SRC dot :file ./assets/posts/dot-internet.png  :cmdline -Kdot -Tpng
digraph {
    // --- config
    graph [rankdir=TB]; // TBLR, top bottom left right, the direction of the graph.
    graph [dpi=150 splines=ortho]; // you can have multiple attrs per statement
    edge[decorate=true]
    node [shape=box];

    // --- definitions
    // nb: setting definitions on their own is useful in larger graphs for standalone attribute setting
    computer [label=computer];
    // quotes are optional, I'm using them when there are spaces
    phone [label="android phone"];
    router [label=router];

    // record syntax: | for horizontal, {|} for vert
    internet [shape=record label="{internet|cat pictures}"]

    // --- relations
    computer -> router;
    phone ->router [label="wifi"];
    router ->internet [dir=both];
}
#+END_SRC

#+RESULTS:
[[file:./assets/posts/dot-internet.png]]