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Graphviz: cluster

A cluster is a subgraph whose ID starts with cluster_.

Labeling clusters

The label attribute labels a cluster. It has no effect, however, in subgraphs. 
digraph L {

   subgraph {
   // This label has no effect:
      label = left
      L1 -> L2
   }

   subgraph cluster_R {
   // This label is in a cluster, so it
   // has an effect and labels the cluster:
      label = right
      R1 -> R2
   }
}
Github repository about-Graphviz, path: /elems/cluster/label.dot

Connecting clusters

An, imho, hackish way to connect clusters is to use the attributes compound, ltail and lhead.
See the demonstration under compound.

See also

Graphviz elements

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