Add igraph example (#4404)

* Add igraph example

* Update comment to mention upcoming igraph release

1 files changed, 44 insertions, 0 deletions

diff --git a/examples/external/plot_igraph.py b/examples/external/plot_igraph.py
new file mode 100644
index 00000000..1e85c7b8
--- /dev/null
+++ b/examples/external/plot_igraph.py
@@ -0,0 +1,44 @@
+"""
+======
+igraph
+======
+
+igraph (https://igraph.org/) is a popular network analysis package that
+provides (among many other things) functions to convert to/from NetworkX.
+"""
+
+import matplotlib.pyplot as plt
+import networkx as nx
+import igraph as ig
+
+# %%
+# NetworkX to igraph
+# ------------------
+
+G = nx.dense_gnm_random_graph(1000, 2000)
+
+# largest connected component
+components = nx.connected_components(G)
+largest_component = max(components, key=len)
+H = G.subgraph(largest_component)
+
+# networkx draw
+nx.draw(H)
+plt.show()
+
+# convert to igraph
+g = ig.Graph.from_networkx(G)
+
+## TODO: uncomment this once python-igraph 0.9 is released
+# igraph draw
+# layout = g.layout()
+# ig.plot(g, layout=layout)
+
+# %%
+# igraph to NetworkX
+# ------------------
+
+g = ig.Graph.GRG(100, 0.2)
+G = g.to_networkx()
+nx.draw(G)
+plt.show()