network visualization with nodes arranged in two columns in MatLab

I have the following matrix including strings in MatLab. This is basically a very simple network, consisting of 4 nodes only. (The original network I am using is a lot larger, but for the sake of simplicity, let's continue using this one.)

A = { '' 'a' '' '' ; 'b' '' 'a' 'b'; '' '' '' 'a' ; 'a' '' '' ''};
dataset({A 'A', 'B', 'C', 'D'}, 'obsnames',{'A', 'B', 'C', 'D'})

Let's say the letters refer to certain link-types between the nodes. Now what I would like to see is two columns of nodes, and the links between them. Also, I would like to visually differentiate between the link types, say, link type 'a' could be red and link type 'b' could be green. I have in mind a layout something like this:

Is there an easy and concise way to do this? I searched through couple of manuals but have not really found this specific kind of network layout with nodes arranged in two columns as shown above.