#contents
http://www.graphviz.org/Documentation/dotguide.pdf
dot -Tgif -o output.gif input.dot
* 単純な有向グラフ
digraph G
{
// 横方向ならLR
rankdir=TB;
from -> to;
}
* 同列に並べる
A -> B;
{rank = same; A; B;}
* 矢印を消す
from -> to [arrowhead = none];
* 配置に影響を与えない
from -> to [constraint = false];
* 複数オプション
from -> to [arrowhead = none, constraint = false];