Graphviz - define the order of the clusters

Question

I'm generating clustered nodes in graphviz/dot. Simplified example:

digraph G {
    rankdir=LR

    n2a->n3
    n1->n2b
    n2b->n2a
    n2b->n3
    n3->n1

    subgraph cluster_1 { label="cluster_1" n1 }
    subgraph cluster_2 { label="cluster_2" n2a n2b }
    subgraph cluster_3 { label="cluster_3" n3 }
}

I want to force dot to always put the clusters in ascending order from right to left (cluster 1 in the left, next is cluster 2 etc.), but to arrange the nodes inside each cluster as dot dictates automatically.

I tried to play with clusterrank, rank, newrank, constraint=false and couldn't manage to make it happen. How can it be done?

Answer 1

You can "force" this to happen by adding edges to establish rank of every node in every cluster. Every node in cluster_1 has a lesser rank than every node in cluster_2, etc. Like so:

digraph G {
    rankdir=LR

    n2a->n3
    n1->n2b
    n2b->n2a
    n2b->n3
    n3->n1

    subgraph cluster_1 { label="cluster_1" n1 }
    subgraph cluster_2 { label="cluster_2" n2a n2b }
    subgraph cluster_3 { label="cluster_3" n3 }
    // simple-minded solution - force clusters based on (added) rank
    edge [style=invis]
    {n1} -> {n2a n2b} -> {n3}
}

Giving: