Write the following into a text file:

A -> B;

B -> C;

C -> A;

A -> D;

D -> C;

C -> B;

And then run the following ruby script with the text file as a command line parameter:

require "win32ole"

def load(fn)

      s = File.new(fn).readlines().join ""

end

gr = WIN32OLE.new "WinGraphviz.DOT"

s = "digraph G {#{load(ARGV[0])}}"

png = gr.ToPNG(s)

png.Save("#{ARGV[0]}.png")

And then you get the following PNG file:

Interesting?

I recently needed to draw a graph (as in connected graph – in graph theory…) and looked around a bit. I came across the Graphviz library developed by the old AT&T. There is a port of the libaray available for windows and it can be downloaded from:

http://www.graphviz.org/

Graphviz or rather, WinGraphviz is available as a COM component which is registered by the installer. So instead of getting my hands dirty with C++,I decided to take the COM bindings in ruby for a walk.

This is where the ruby code comes – it creates an object of WinGraphviz.DOT component and uses it to create a graph. Notice how I can interact with a COM object as though it were a regular Ruby object – fun fun.

As for the language in the text file – Graphviz graphs can be specified using a language (you can find a spec on their website). The A-> B etc at the beginning of the blog post was simply a subset of this language.

Of course if your data is in some other format, you will have to translate it into the graph language – but then again if its in an excel file or something you can just use Ruby to talk to excel COM component and read the data out and then talk to the Graphviz component.