Vertical and horizontal headers with Graphviz

Question

I need to create a vertical and horizontal header with Graphviz, but I do not know how to make the two subgraphs have different orientation. I have tried with rankdir but apparently it does not work with subgraphs. I have no idea how to proceed. I appreciate any help.

digraph Table{
    node[shape=box style=filled fillcolor=olivedrab2]
    //rankdir=TB
    subgraph Rows{
     rankdir=TB
     A[label="A"]
     B[label="B"]
     C[label="C"]
     D[label="D"]
     E[label="E"]
     F[label="F"]       
     A->B
     B->A
     B->C
     C->B
     C->D
     D->C
     D->E
     E->D
     E->F
     F->E
     {rank=same A B C D E F}
 }
subgraph Column{
    rankdir=LR
    M[label="M"]
    N[label="N"]
    O[label="O"]
    P[label="P"]
    Q[label="Q"]
    R[label="R"]        
    M->N
    //N->M
    N->O
    //O->N
    O->P
    //P->O
    P->Q
    //Q->P
    Q->R
    //R->Q
    {rank=same M N O P Q R}
  }
 }

Something like this

Answer 1

You almost did everything right. Just remove the {rank=same MNOPQR} line.

You are correct, rankdir works only for the whole graph, it won't work for subgraphs separately. But you can control position of nodes using:

• rank =same attribute of subgraph

which forces all nodes mentioned in subgraph to be at the same level.

• constraint =false attribute of an edge

which allows you to connect two nodes but not affect their position by this connection.