Simplify ¶
Simplify¶
This example shows how to remove self loops and multiple edges using simplify()
.
We start with a graph that includes loops and multiedges:
import igraph as ig
import matplotlib.pyplot as plt
# Generate graph with multiple edges and loops
g1 = ig.Graph([
(0, 1),
(1, 2),
(2, 3),
(3, 4),
(4, 0),
(0, 0),
(1, 4),
(1, 4),
(0, 2),
(2, 4),
(2, 4),
(2, 4),
(3, 3)],
)
To get rid of both loops and multiedges, we make a copy of the graph and simplify it in place:
# Generate simplified version of graph
g2 = g1.copy()
g2.simplify()
Finally, we check what happened by plotting both graphs:
# Plot graphs
visual_style = {
"vertex_color": "lightblue",
"vertex_size": 0.4,
"vertex_label": [0, 1, 2, 3, 4],
}
# Make twin axes
fig, axs = plt.subplots(1, 2, sharex=True, sharey=True)
# Plot graphs
ig.plot(
g1,
layout="circle",
target=axs[0],
**visual_style,
)
ig.plot(
g2,
layout="circle",
target=axs[1],
**visual_style,
)
# Draw rectangles around axes
axs[0].add_patch(plt.Rectangle(
(0, 0), 1, 1, fc='none', ec='k', lw=4, transform=axs[0].transAxes,
))
axs[1].add_patch(plt.Rectangle(
(0, 0), 1, 1, fc='none', ec='k', lw=4, transform=axs[1].transAxes,
))
# Set titles
axs[0].set_title('Multigraph...')
axs[1].set_title('...simplified')
plt.show()

The original graph (left) versus the simplified graph (right).¶