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You need to define the “weight” attribute to the edges.
This way any function or class that accepts the "weights=None” attribute will be able to retrieve the weights of the connections.
In a weighted graph, Shortest paths means paths with minimum sum of edge weights (path length).
g = Graph()
g.add_vertices(7)
g.add_edge(0,1)
g.add_edge(0,2)
g.add_edge(1,3)
g.add_edge(2,3)
g.add_edge(5,4)
g.add_edge(5,6)
g.add_edge(6,4)
g.es['weight'] = [2,1,3,5,2,3,1]
clust = g.clusters()
for c in clust:
print("subgraph:")
gcomponent=g.subgraph(c)
u=next(iter(gcomponent.vs))
paths=gcomponent.get_shortest_paths(u,to=None,weights=None,mode='ALL',output="vpath")
print(paths)
Sure, here it is:
g.add_vertices(7)
g.add_edge(0,1,n=2)
g.add_edge(0,2,n=1)
g.add_edge(1,3,n=3)
g.add_edge(2,3,n=5)
g.add_edge(5,4,n=2)
g.add_edge(5,6,n=3)
g.add_edge(6,4,n=1)
clust = g.clusters()
for c in clust:
print("subgraph:")
gcomponent=g.subgraph(c)
u=next(iter(gcomponent.vs))
paths=gcomponent.get_shortest_paths(u,to=None,weights=None,mode=ig.ALL,output="vpath")
print(paths)
Thank you very much!
Could you also add the actual graph weights and the full code so that we can reproduce this?
Hello,
I would like to ask a question about the "get_shortest_paths" function in python-igraph. Could you explain what is the impact of adding edge weights when calculating path lengths? I had a very interesting occurrence that I couldn't explain why:
Case 1: edge weights are nonzero (an attribute of edges)
Result: [[], [0, 1], [0, 2], [0, 1, 3]]
Case 2: edge weights are None
Result: [[0], [0, 1], [0, 2], [0, 1, 3]]
why does the first entry change like this?=O
My code is here:
clust = g1.clusters()
for c in clust:
print("subgraph:")
gcomponent=g1.subgraph(c)
u=next(iter(gcomponent.vs))
paths=gcomponent.get_shortest_paths(u,to=None,weights=None,mode=ig.ALL,output="vpath")
print(paths)
in which only the weights=None part is changed between the cases.
I would appreciate if you could provide meaning to this!
Thank you very much!
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