LayeredGraphPlot: two instances of the same label

Question

What I'd like to do is to have the same label more than once in the plot. I.e. I do not want the edges to direct toward the first instance of that label! For example:

LayeredGraphPlot[{1 -> 2, 1 -> 3, 2 -> 3, 1 -> 4, 2 -> 4, 3 -> 2}, VertexLabeling -> True]

I want 3 -> 2 (a new 2)!

How can this be achieved?

Answer 1

You have to identify the vertices uniquely, so I would call the second instance of 2 by the name 5 instead. But you can label them differently using this:

Clear[label];
label[5] = 2;

LayeredGraphPlot[{1 -> 2, 1 -> 3, 2 -> 3, 1 -> 4, 2 -> 4, 3 -> 5}, 
 VertexLabeling -> True, 
 VertexRenderingFunction -> 
  Function[{p, l}, 
   Text[Framed[If[ValueQ[label[l]], label[l], l], 
     Background -> RGBColor[1, 1, 0.8`], 
     FrameStyle -> RGBColor[0.94`, 0.85`, 0.36`]], p]]]

The VertexRenderingFunction option contains the same style as the default vertex labels, but instead of the vertex number supplied to it as the second argument l, it outputs the value of label[l]. The latter can be defined for any vertex number that you want to appear with a different label. If label[x] isn't defined, then ValueQ returns False and the label is displayed in the default form as x.

Answer 2

Latest graph functionality works as well. You could define the graph structure you need :

g = Graph[{1 -> 2, 1 -> 3, 2 -> 3, 1 -> 4, 2 -> 4, 3 -> 5}, 
   GraphLayout -> "LayeredDigraphEmbedding", VertexLabels -> "Name"];

and then relabel the part you need to be different:

SetProperty[{g, 5}, VertexLabels -> 2]