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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/bipartite/matrix.py')
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diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/bipartite/matrix.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/bipartite/matrix.py new file mode 100644 index 00000000..bbfa47c7 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/bipartite/matrix.py @@ -0,0 +1,168 @@ +""" +==================== +Biadjacency matrices +==================== +""" + +import itertools + +import networkx as nx +from networkx.convert_matrix import _generate_weighted_edges + +__all__ = ["biadjacency_matrix", "from_biadjacency_matrix"] + + +@nx._dispatchable(edge_attrs="weight") +def biadjacency_matrix( + G, row_order, column_order=None, dtype=None, weight="weight", format="csr" +): + r"""Returns the biadjacency matrix of the bipartite graph G. + + Let `G = (U, V, E)` be a bipartite graph with node sets + `U = u_{1},...,u_{r}` and `V = v_{1},...,v_{s}`. The biadjacency + matrix [1]_ is the `r` x `s` matrix `B` in which `b_{i,j} = 1` + if, and only if, `(u_i, v_j) \in E`. If the parameter `weight` is + not `None` and matches the name of an edge attribute, its value is + used instead of 1. + + Parameters + ---------- + G : graph + A NetworkX graph + + row_order : list of nodes + The rows of the matrix are ordered according to the list of nodes. + + column_order : list, optional + The columns of the matrix are ordered according to the list of nodes. + If column_order is None, then the ordering of columns is arbitrary. + + dtype : NumPy data-type, optional + A valid NumPy dtype used to initialize the array. If None, then the + NumPy default is used. + + weight : string or None, optional (default='weight') + The edge data key used to provide each value in the matrix. + If None, then each edge has weight 1. + + format : str in {'bsr', 'csr', 'csc', 'coo', 'lil', 'dia', 'dok'} + The type of the matrix to be returned (default 'csr'). For + some algorithms different implementations of sparse matrices + can perform better. See [2]_ for details. + + Returns + ------- + M : SciPy sparse array + Biadjacency matrix representation of the bipartite graph G. + + Notes + ----- + No attempt is made to check that the input graph is bipartite. + + For directed bipartite graphs only successors are considered as neighbors. + To obtain an adjacency matrix with ones (or weight values) for both + predecessors and successors you have to generate two biadjacency matrices + where the rows of one of them are the columns of the other, and then add + one to the transpose of the other. + + See Also + -------- + adjacency_matrix + from_biadjacency_matrix + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Adjacency_matrix#Adjacency_matrix_of_a_bipartite_graph + .. [2] Scipy Dev. References, "Sparse Matrices", + https://docs.scipy.org/doc/scipy/reference/sparse.html + """ + import scipy as sp + + nlen = len(row_order) + if nlen == 0: + raise nx.NetworkXError("row_order is empty list") + if len(row_order) != len(set(row_order)): + msg = "Ambiguous ordering: `row_order` contained duplicates." + raise nx.NetworkXError(msg) + if column_order is None: + column_order = list(set(G) - set(row_order)) + mlen = len(column_order) + if len(column_order) != len(set(column_order)): + msg = "Ambiguous ordering: `column_order` contained duplicates." + raise nx.NetworkXError(msg) + + row_index = dict(zip(row_order, itertools.count())) + col_index = dict(zip(column_order, itertools.count())) + + if G.number_of_edges() == 0: + row, col, data = [], [], [] + else: + row, col, data = zip( + *( + (row_index[u], col_index[v], d.get(weight, 1)) + for u, v, d in G.edges(row_order, data=True) + if u in row_index and v in col_index + ) + ) + A = sp.sparse.coo_array((data, (row, col)), shape=(nlen, mlen), dtype=dtype) + try: + return A.asformat(format) + except ValueError as err: + raise nx.NetworkXError(f"Unknown sparse array format: {format}") from err + + +@nx._dispatchable(graphs=None, returns_graph=True) +def from_biadjacency_matrix(A, create_using=None, edge_attribute="weight"): + r"""Creates a new bipartite graph from a biadjacency matrix given as a + SciPy sparse array. + + Parameters + ---------- + A: scipy sparse array + A biadjacency matrix representation of a graph + + create_using: NetworkX graph + Use specified graph for result. The default is Graph() + + edge_attribute: string + Name of edge attribute to store matrix numeric value. The data will + have the same type as the matrix entry (int, float, (real,imag)). + + Notes + ----- + The nodes are labeled with the attribute `bipartite` set to an integer + 0 or 1 representing membership in part 0 or part 1 of the bipartite graph. + + If `create_using` is an instance of :class:`networkx.MultiGraph` or + :class:`networkx.MultiDiGraph` and the entries of `A` are of + type :class:`int`, then this function returns a multigraph (of the same + type as `create_using`) with parallel edges. In this case, `edge_attribute` + will be ignored. + + See Also + -------- + biadjacency_matrix + from_numpy_array + + References + ---------- + [1] https://en.wikipedia.org/wiki/Adjacency_matrix#Adjacency_matrix_of_a_bipartite_graph + """ + G = nx.empty_graph(0, create_using) + n, m = A.shape + # Make sure we get even the isolated nodes of the graph. + G.add_nodes_from(range(n), bipartite=0) + G.add_nodes_from(range(n, n + m), bipartite=1) + # Create an iterable over (u, v, w) triples and for each triple, add an + # edge from u to v with weight w. + triples = ((u, n + v, d) for (u, v, d) in _generate_weighted_edges(A)) + # If the entries in the adjacency matrix are integers and the graph is a + # multigraph, then create parallel edges, each with weight 1, for each + # entry in the adjacency matrix. Otherwise, create one edge for each + # positive entry in the adjacency matrix and set the weight of that edge to + # be the entry in the matrix. + if A.dtype.kind in ("i", "u") and G.is_multigraph(): + chain = itertools.chain.from_iterable + triples = chain(((u, v, 1) for d in range(w)) for (u, v, w) in triples) + G.add_weighted_edges_from(triples, weight=edge_attribute) + return G |