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How can I have pair of edges between nodes in this kind of graphs?

cities = CityData[{All, #}] & /@ {"Germany"}; bigcities = 
Select[Select[Join @@ cities, FreeQ[#, ""] &], 
CityData[#, "Population"] > 100000 &];
cityCoords = 
Select[CityData[#, "Coordinates"] & /@ bigcities, FreeQ[#, ""] &];
Needs["ComputationalGeometry`"];
pts = Reverse[cityCoords, 2];
dt = DelaunayTriangulation[pts];
toPairs[{m_, ns_List}] := Map[{m, #} &, ns];
edges = Union[Sort /@ Flatten[toPairs /@ dt, 1]];
Graph[edges, ImagePadding -> 20, 
VertexCoordinates -> pts, VertexStyle -> LightBlue, 
VertexLabels -> bigcities[[All, 1]], 
Prolog -> {LightBrown, EdgeForm[{Thick, Black}], 
CountryData["Germany", "FullPolygon"]}, ImageSize -> 800]
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up vote 3 down vote accepted

Just use DirectedGraph. At default, that will replace undirected edge to a pair of directed edges.

enter image description here

share|improve this answer
    
hamir Thanks.Now I am embarrassed!! – Alex Sep 24 '13 at 19:21

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