Specified edge lengths on networkx/igraph (Python)

Question

I wanted to visualize a network with the data I have and would like to graph them with specific edge lengths. I use Python, and I've tried networkx and igraph to plot but all seem to assign fixed edge lengths.

a.) I wonder if I did the codes wrong or the packages aren't really capable. How do you properly implement specified edge lengths for networkx or igraph?

b.) If networkx and igraph can't do it, what package could you possibly suggest? (Preferably one that can carry over 80 thousand nodes.)

Thanks!

Answer 1

This should work:

import networkx as NX
import pygraphviz as PG

G = PG.AGraph()
nlist = "A B C D E".split()
a, b = "A A B", "B C D"
elist = zip(a.split(), b.split())

G.add_nodes_from(nlist)
G.add_nodes_from(elist)
G.node_attr.update(color="red", style="filled")
G.edge_attr.update(color="blue", len="2.0", width="2.0")

print(G.edge_attr)
# returns {'color': 'red', 'width': '', 'len': '2.0'}

# add new edge with custom length (all others have length=2.0):
G.add_edge("C", "E", len="3.0", color="blue, width="2.0")

edge = G.get_edge("C", "E")
print(edge_attr)
# returns {'color': 'blue', 'width': '2.0', 'len': '3.0'}

# and you can confirm that introspection by drawing & printing this graph:
G.draw('somefilename', format='png', prog='neato')

Most graph drawing algorithms use some version of SMACOF, which of course varies the edge length; however, the graphviz layout engine 'neato' (supplied as the 2nd argument to 'draw' above) ought to preserve, if at all possible, user-set edge lengths.

The library i used here is certainly sturdy enough to handle 80,000 nodes.