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import pytest
pytest.importorskip("scipy")
import networkx as nx
from networkx.algorithms.bipartite import spectral_bipartivity as sb
# Examples from Figure 1
# E. Estrada and J. A. Rodríguez-Velázquez, "Spectral measures of
# bipartivity in complex networks", PhysRev E 72, 046105 (2005)
class TestSpectralBipartivity:
def test_star_like(self):
# star-like
G = nx.star_graph(2)
G.add_edge(1, 2)
assert sb(G) == pytest.approx(0.843, abs=1e-3)
G = nx.star_graph(3)
G.add_edge(1, 2)
assert sb(G) == pytest.approx(0.871, abs=1e-3)
G = nx.star_graph(4)
G.add_edge(1, 2)
assert sb(G) == pytest.approx(0.890, abs=1e-3)
def test_k23_like(self):
# K2,3-like
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(0, 1)
assert sb(G) == pytest.approx(0.769, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
assert sb(G) == pytest.approx(0.829, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
G.add_edge(3, 4)
assert sb(G) == pytest.approx(0.731, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(0, 1)
G.add_edge(2, 4)
assert sb(G) == pytest.approx(0.692, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
G.add_edge(3, 4)
G.add_edge(0, 1)
assert sb(G) == pytest.approx(0.645, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
G.add_edge(3, 4)
G.add_edge(2, 3)
assert sb(G) == pytest.approx(0.645, abs=1e-3)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
G.add_edge(3, 4)
G.add_edge(2, 3)
G.add_edge(0, 1)
assert sb(G) == pytest.approx(0.597, abs=1e-3)
def test_single_nodes(self):
# single nodes
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(2, 4)
sbn = sb(G, nodes=[1, 2])
assert sbn[1] == pytest.approx(0.85, abs=1e-2)
assert sbn[2] == pytest.approx(0.77, abs=1e-2)
G = nx.complete_bipartite_graph(2, 3)
G.add_edge(0, 1)
sbn = sb(G, nodes=[1, 2])
assert sbn[1] == pytest.approx(0.73, abs=1e-2)
assert sbn[2] == pytest.approx(0.82, abs=1e-2)
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