How to Replace EdgeLabel in a Graph

Question

I am working with Graphs in which I want to define a Graph with Symbols or Strings as EdgeLabels, and later replace these with functions of the symbols with symbols then replaced with numerical values. I have tried using Replace without success. I can replace the symbols with numerical values by setting the values of the symbols, but that does not allow for replacing the symbol by a function of the symbol first.

Below are my unsuccessful attempts:

g = Graph[{1 \[DirectedEdge] 2, 2 \[DirectedEdge] 3}, 
  EdgeLabels -> {1 \[DirectedEdge] 2 -> x, 2 \[DirectedEdge] 3 -> y}]
g // FullForm
(replacements doesn't work)
values = {x -> 1, y -> 2};
g /. values
(a more complicated case)
g /. Rule[DirectedEdge[n1_, n2_], s_] -> 
  Rule[DirectedEdge[n1, n2], 1/s]
(this does work, but doesn't fulfill the need for more complicated 

replacements)
x = z;
g

Does this answer your question? How do I replace expressions inside a Graph object? Also: #4543 — Domen, Mar 09 '24 at 17:28

kglr · Accepted Answer · 2024-03-09T18:15:40.623

3

You can use

Graph[g, EdgeLabels -> PropertyValue[g, EdgeLabels] /. values]

or

SetProperty[g, EdgeLabels -> PropertyValue[g, EdgeLabels] /. values]

to get

Similarly, for the second example:

values2 = Rule[DirectedEdge[n1_, n2_], s_] :> 
   Rule[DirectedEdge[n1, n2], 1/s];
Graph[g, EdgeLabels -> PropertyValue[g, EdgeLabels] /. values2]

edited Mar 09 '24 at 18:15

answered Mar 09 '24 at 17:28

kglr

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Brilliant! Thank you @kglr – David Keith Mar 09 '24 at 19:33

How to Replace EdgeLabel in a Graph

1 Answers1