somewhat brute force solution to the question raised in this tweet: https://twitter.com/silentbicycle/status/418760644066676736 output from `dot -Tpng figure2.gv` at http://ow.ly/i/4bZ8B

figure2.gv

digraph fig2 {
  splines=line # makes edges straight rather than curved
  ranksep=0.2  # controls distance between rows

  # create a record-type node representing the row of numbers
  # (the `<x>` bit declares a port we can point edges to)
  n [shape=record label="{<a>58}|{<b>82}|{<c>16}|{<d>85}|{<e>65}|{<f>5}|{<g>67}|{<h>26}"]

  # create some dummy rows, each with one false node per element in n
  node [shape=point height=0 style=invis];
  { rank=same; fa1;fb1;fc1;fd1;fe1;ff1;fg1;fh1; }
  { rank=same; fa2;fb2;fc2;fd2;fe2;ff2;fg2;fh2; }
  { rank=same; fa3;fb3;fc3;fd3;fe3;ff3;fg3;fh3; }
  edge [style=invis]
  n:a -> fa1 -> fa2 -> fa3
  n:b -> fb1 -> fb2 -> fb3
  n:c -> fc1 -> fc2 -> fc3
  n:d -> fd1 -> fd2 -> fd3
  n:e -> fe1 -> fe2 -> fe3
  n:f -> ff1 -> ff2 -> ff3
  n:g -> fg1 -> fg2 -> fg3
  n:h -> fh1 -> fh2 -> fh3

  # create the subsequence edges
  edge [dir=none style=bold constraint=false] # no arrows, fat lines, don't change node placement

  edge [color=black] # first subsequence
  fa1 -> n:a         # vertical lines
  fd1 -> n:d
  fg1 -> n:g
  fa1 -> fd1 -> fg1  # horizontal line

  edge [color=blue]  # second subsequence
  fb2 -> n:b         # vertical lines
  fe2 -> n:e
  fh2 -> n:h
  fb2 -> fe2 -> fh2  # horizontal line

  edge [color=red]   # third subsequence
  fc3 -> n:c         # vertical lines
  ff3 -> n:f
  fc3 -> ff3         # horizontal line

  # create a legend
  subgraph clusterLegend {
    pencolor=transparent # hide the line around the cluster

    # create "head" nodes to contain the label text
    node [shape=plaintext style="" width=2 fontsize=12 fontname=Helvetica]
    l1h [label="first subsequence\l" fontcolor=black]
    l2h [label="second subsequence\l" fontcolor=blue]
    l3h [label="third subsequence\l" fontcolor=red]

    # create the corresponding "tail" nodes and edges
    node [shape="point" width=0 style=invis]
    edge [dir=none style=bold constraint=false minlen=1]
    l1t -> l1h [color=black]
    l2t -> l2h [color=blue]
    l3t -> l3h [color=red]

    # ensure that the labels are stacked top-to-bottom
    edge [style=invis constraint=true minlen=""]
    l1t -> l2t -> l3t
    l1h -> l2h -> l3h
  }

  # create a dummy edge to ensure the legend is placed below the figure
  fb3 -> l1t [style=invis constraint=true minlen=2]

}