Better layout of nodes for block diagrams in dot

Question

After a previous question (Block diagram layout with dot/Graphviz) I have further questions. The following is compiled like so:

dot -Gsplines=none test.gv | neato -n -Gsplines=ortho -Tpng -otest.png

digraph G {
    graph [rankdir = LR];

    node[shape=record, style=filled];

bar[label="Bar", height=1.3636363636363635];
tea[label="Tea", height=1.3636363636363635];
brew[label="Brew", height=3.6363636363636362];
bar1[label="Bar1", height=2.2727272727272725];
baz[label="Baz", height=1];
foo[label="Foo", height=5.0];
darjeeling[label="Darjeeling", height=3.1818181818181817];
example[label="Example", height=17.727272727272727];

bar -> example [label="bar_clk"];
bar -> example [label="bar_bar"];
example -> tea [label="bli1"];
example -> tea [label="blo2"];
example -> tea [label="blo3"];
example -> brew [label="bli"];
example -> brew [label="blo"];
example -> brew [label="blo"];
example -> brew [label="blo"];
example -> brew [label="blo"];
example -> brew [label="blo"];
example -> brew [label="blo"];
example -> brew [label="blo"];
bar1 -> example [label="bar1_foo"];
bar1 -> example [label="bar1_bar"];
bar1 -> example [label="bar1_baz"];
bar1 -> example [label="bar1_baz1"];
bar1 -> example [label="bar1_bar2"];
baz -> example [label="baz_foo"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> foo [label="bla"];
example -> bar [label="blu"];
example -> baz [label="ble"];
darjeeling -> example [label="darjeeling_bli1"];
darjeeling -> example [label="darjeeling_blo2"];
darjeeling -> example [label="darjeeling_blo3"];
darjeeling -> example [label="darjeeling_bli1"];
darjeeling -> example [label="darjeeling_blo2"];
example -> darjeeling [label="bla"];
darjeeling -> example [label="darjeeling_blo3"];
}

My question is how I could take the, say, Baz and Darjeeling nodes and move them to the left side to decrease the height of the middle node. I don't know what determines this. I understand this is a directional graph, so the general "flow" of the diagram is left to right, I'd just like more control.

These diagrams will be generated automatically, so an explanation on how to lay it out as I wish and why, as opposed to a code snippet that makes it work for this particular example, is preferred.

marapet · Accepted Answer · 2011-11-08T11:13:39.010

A couple of points:

how I could take the, say, Baz and Darjeeling nodes and move them to the left side

By setting constraint=false for the edges going from Example to Baz and Darjeeling, or by grouping all the nodes to appear left of Example in a subgraph with rank=min.

You may say that this is not a suitable solution (at least not the one with constraint=false) because

These diagrams will be generated automatically

and I completely understand (been there many times) - but at the same time, you wish

to decrease the height of the middle node

which is set manually, so the graph still is not fully auto-generated (how do you calculate the height needed for Example?).

I don't know what determines this

I'm not completely sure neither - Baz could might as well be on the left.

Surprisingly, the order of appearance of the nodes changes the layout in some cases. For example, if you move up the definition of the Darjeeling node, it will appear on the left side (and Bar gets to be at the right side).

Edit: Here comes the code snippet...

A third possibility is to define all edges in the right order (top-down/left-right) and decorate the edges going back with dir=back.

If you change these 3 lines

example -> bar [label="blu"];
example -> baz [label="ble"];
example -> darjeeling [label="bla"];

into

bar -> example [label="blu", dir=back];
baz -> example [label="ble", dir=back];
darjeeling -> example [label="bla", dir=back];

or into

example -> bar [label="blu", constraint=false];
example -> baz [label="ble", constraint=false];
example -> darjeeling [label="bla", constraint=false];

(and change the height of example)

You'll get

graphviz result

Thanks for the answer. A subgraph may work. I can also put some constraint=false things in there, just need to play with it some. The height is now computed based on the number of edges to it; that's easily changed though. I was aware of changing order, but didn't get the sides more balanced. Will play with subgraphs and report, thanks! — Christoph, Nov 08 '11 at 03:37
Sorry for the late answer. This looks very promising so it's the accepted answer! — Christoph, Nov 15 '11 at 22:39

Better layout of nodes for block diagrams in dot

1 Answers1