# Swapping elements of list

Say I have a directed graph inputted in the following format in Mathematica:

g = {{1, “a”, 2}, {2, “b”, 1}}

I’d like to plot this graph using GraphPlot in Mathematica, which is the following syntax:

GraphPlot[{{1 -> 2, “a”}, {2 -> 1, “b”}}, VertexLabeling -> True, DirectedEdges -> True,
VertexCoordinateRules -> Auto, VertexLabeling -> True]

How would I swap the middle elements and the last elements in any list like g, so that g would look closer to the argument of GraphPlot?

{{1 -> 2, “a”}, {2 -> 1, “b”}}

I have searched the Mathematica documentation but was unable to find a good way of doing this.

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All you need is a simple replacement rule: g /. {f_Integer, m_String, l_Integer} :> {f -> l, m}
– R. M.♦
Oct 28 ’13 at 3:48

Thanks! That was really simple and clean.
– user10245
Oct 28 ’13 at 5:00

Also g[[All, 1]] = Rule @@@ g[[All, {1, 3}]];g[[All, {1, 2}]]
– Mike Honeychurch
Oct 28 ’13 at 5:26

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2

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rm -rf has suggested the simplest solution which matches the elements and swaps them around:

g = {{1, “a”, 2}, {2, “b”, 1}};
g /. {a_Integer, b_String, c_Integer} :> {a -> c, b}
{{1 -> 2, “a”}, {2 -> 1, “b”}}

Graph[Labeled[#1 \[DirectedEdge] #3, Style[#2, 20]] & @@@ g]

or with more formatting:

Graph[Labeled[#1 \[DirectedEdge] #3, Style[#2, 20]] & @@@ g,
VertexLabels -> Placed[“Name”, Center], VertexSize -> 0.2,
VertexLabelStyle -> 20]

Thanks for this– yes, this also works, but alas I can only accept one answer.
– user10245
Oct 28 ’13 at 5:00