How to get connected neighbour nodes on the same height when drawing in GraphViz?

Question

I'm trying to draw the following (suffix-tree) using GraphViz:

digraph G {
  1[label = " "];
  2[label = " "];
  3[label = " "];
  4[label = " "];
  5[label = " "];
  6[label = " "];
  7[label = " "];
  8[label = " "];

  // edges drawn vertically, all fine.
  1 -> 2 [label="ab"];
  1 -> 3 [label=" b"];
  1 -> 4 [label=" c$"];
  2 -> 5 [label="abc$"];
  2 -> 6 [label="c$"];
  3 -> 7 [label=" abc$"];
  3 -> 8 [label="c$"];

  // node 3 should be on the right side of node 2, and
  // a cross line should be drawn horizontally

  2 -> 3 [style=dotted,label="abc$"];

}

The problem is, that the node reached by following edges "abc$" and "b" is not on the same height like those 2 nodes reached by following "ab" and "c$".

Has annyone encountered the same situation and could share a solution?

Answer 1

Ah well, didnt search for the proper terms! "placing nodes on a horizontal line", offers a solution.

This code now positions the nodes 2,3,4 properly on the same "horizontal line".

digraph G {
  1[label = " "];
  2[label = " "];
  3[label = " "];
  4[label = " "];
  5[label = " "];
  6[label = " "];
  7[label = " "];
  8[label = " "];

  node[group=sameheight];
    { rank = same; 2; 3; 4; }

  1 -> 2 [label="ab"];
  1 -> 3 [label=" b"];
  1 -> 4 [label=" c$"];
  2 -> 3 [style=dotted];
  2 -> 5 [label="abc$"];
  2 -> 6 [label="c$"];
  3 -> 7 [label=" abc$"];
  3 -> 8 [label="c$"];
}

Hope it helps someone.