How to force two nodes to be side by side?

Question

I made a graph using dot -Tsvg.

This is the dot language file i made:

digraph genealogy {
    size = "7,7";
    node [fontsize = "10", shape = "box", style="filled", fillcolor="aquamarine"];
    p1 [ fillcolor="aquamarine", label="node" ];
    p2 [ fillcolor="aquamarine", label="node" ];
    p3 [ fillcolor="aquamarine", label="node" ];
    p4 [ fillcolor="aquamarine", label="node" ];
    p5 [ fillcolor="aquamarine", label="node" ];
    p6 [ fillcolor="aquamarine", label="node" ];
    p7 [ fillcolor="aquamarine", label="node" ];
    p8 [ fillcolor="aquamarine", label="node" ];
    p9 [ fillcolor="aquamarine", label="node" ];
    p11 [ fillcolor="aquamarine", label="node" ];
    p12 [ fillcolor="aquamarine", label="node" ];
    p13 [ fillcolor="aquamarine", label="node" ];
    p16 [ fillcolor="aquamarine", label="node" ];
    p17 [ fillcolor="aquamarine", label="node" ];
    b1 [ shape = "point", style="filled", fillcolor="white" ];
    p3 -> b1 [arrowhead = "none", color="red"];
    b2 [ shape = "point", style="filled", fillcolor="white" ];
    p2 -> b2 [arrowhead = "none", color="red"];
    p3 -> b2 [arrowhead = "none", color="red"];
    b3 [ shape = "point", style="filled", fillcolor="white" ];
    p4 -> b3 [arrowhead = "none", color="red"];
    p5 -> b3 [arrowhead = "none", color="red"];
    b4 [ shape = "point", style="filled", fillcolor="white" ];
    p6 -> b4 [arrowhead = "none", color="red"];
    p11 -> b4 [arrowhead = "none", color="red"];
    b2 -> p1 [arrowhead = "onormal", color="red"];
    b3 -> p2 [arrowhead = "onormal", color="red"];
    b3 -> p6 [arrowhead = "onormal", color="red"];
    b3 -> p7 [arrowhead = "onormal", color="red"];
    b4 -> p8 [arrowhead = "onormal", color="red"];
    b4 -> p9 [arrowhead = "onormal", color="red"];
    b1 -> p12 [arrowhead = "onormal", color="red"];
    b1 -> p13 [arrowhead = "onormal", color="red"];
    b1 -> p16 [arrowhead = "onormal", color="red"];
    p4 -> p5 [dir="none", arrowhead = "none",  color="blue"];
    p7 -> p17 [dir="none", arrowhead = "none",  color="blue"];
}

This is the result:

I would like to force the nodes connected by a blue line to be side by side (horizontal), and not under each other or at another crazy position.

Is this possible?

Sense

Answer 1

You can make use of rank attribute. Setting rank="same" or rank="source" may be helpfui. This places the two nodes on the same rank or lowest rank. Here is one of the possibilities:

digraph genealogy {
    size = "7,7";
    node [fontsize = "10", shape = "box", style="filled", fillcolor="aquamarine"];

    subgraph _1 {
     rank="same";
     p4 [ fillcolor="aquamarine", label="node" ];
     p5 [ fillcolor="aquamarine", label="node" ];
     p4 -> p5 [dir="none", arrowhead = "none",  color="blue"];
}
    subgraph _2 {   
    rank="source";  
    p7 [ fillcolor="aquamarine", label="node" ];
    p17 [ fillcolor="aquamarine", label="node" ];
    p7 -> p17 [dir="none", arrowhead = "none",  color="blue"];
}

p1 [ fillcolor="aquamarine", label="node" ];
p2 [ fillcolor="aquamarine", label="node" ];
p3 [ fillcolor="aquamarine", label="node" ];
p6 [ fillcolor="aquamarine", label="node" ];
p8 [ fillcolor="aquamarine", label="node" ];
p9 [ fillcolor="aquamarine", label="node" ];
p11 [ fillcolor="aquamarine", label="node" ];
p12 [ fillcolor="aquamarine", label="node" ];
p13 [ fillcolor="aquamarine", label="node" ];
p16 [ fillcolor="aquamarine", label="node" ];
b1 [ shape = "point", style="filled", fillcolor="white" ];
p3 -> b1 [arrowhead = "none", color="red"];
b2 [ shape = "point", style="filled", fillcolor="white" ];
p2 -> b2 [arrowhead = "none", color="red"];
p3 -> b2 [arrowhead = "none", color="red"];
b3 [ shape = "point", style="filled", fillcolor="white" ];
p4 -> b3 [arrowhead = "none", color="red"];
p5 -> b3 [arrowhead = "none", color="red"];
b4 [ shape = "point", style="filled", fillcolor="white" ];
p6 -> b4 [arrowhead = "none", color="red"];
p11 -> b4 [arrowhead = "none", color="red"];
b2 -> p1 [arrowhead = "onormal", color="red"];
b3 -> p2 [arrowhead = "onormal", color="red"];
b3 -> p6 [arrowhead = "onormal", color="red"];
b3 -> p7 [arrowhead = "onormal", color="red"];
b4 -> p8 [arrowhead = "onormal", color="red"];
b4 -> p9 [arrowhead = "onormal", color="red"];
b1 -> p12 [arrowhead = "onormal", color="red"];
b1 -> p13 [arrowhead = "onormal", color="red"];
b1 -> p16 [arrowhead = "onormal", color="red"];

}

Calculating

Answer 2

Just to shorten the other answer: Put the nodes you want to be the side by side inside a sub-graph graph with rank="same" option.

before:

digraph G {
A, B
    //subgraph {
    //  rank="same"
        C, D
    //}
A -> B -> C -> D
}

after:

digraph G {
A, B
    subgraph {
        rank="same"
        C, D
    }
A -> B -> C -> D
}

Micky