Source code for karateclub.graph_embedding.sf

import numpy as np
import networkx as nx
from typing import List
from scipy.sparse.linalg import eigsh
from karateclub.estimator import Estimator

[docs]class SF(Estimator): r"""An implementation of `"SF" <https://arxiv.org/abs/1810.09155>`_ from the NeurIPS Relational Representation Learning Workshop '18 paper "A Simple Baseline Algorithm for Graph Classification". The procedure calculates the k lowest egeinvalues of the normalized Laplacian. If the graph has a lower number of eigenvalues than k the representation is padded with zeros. Args: dimensions (int): Number of lowest eigenvalues. Default is 128. seed (int): Random seed value. Default is 42. """ def __init__(self, dimensions: int = 128, seed: int = 42): self.dimensions = dimensions self.seed = seed def _calculate_sf(self, graph): """ Calculating the features of a graph. Arg types: * **graph** *(NetworkX graph)* - A graph to be embedded. Return types: * **embedding** *(Numpy array)* - The embedding of a single graph. """ number_of_nodes = graph.number_of_nodes() L_tilde = nx.normalized_laplacian_matrix(graph, nodelist=range(number_of_nodes)) if number_of_nodes <= self.dimensions: embedding = eigsh( L_tilde, k=number_of_nodes - 1, which="LM", ncv=10 * self.dimensions, return_eigenvectors=False, ) shape_diff = self.dimensions - embedding.shape - 1 embedding = np.pad( embedding, (1, shape_diff), "constant", constant_values=0 ) else: embedding = eigsh( L_tilde, k=self.dimensions, which="LM", ncv=10 * self.dimensions, return_eigenvectors=False, ) return embedding
[docs] def fit(self, graphs): """ Fitting an SF model. Arg types: * **graphs** *(List of NetworkX graphs)* - The graphs to be embedded. """ self._set_seed() graphs = self._check_graphs(graphs) self._embedding = [self._calculate_sf(graph) for graph in graphs]
[docs] def get_embedding(self) -> np.array: r"""Getting the embedding of graphs. Return types: * **embedding** *(Numpy array)* - The embedding of graphs. """ return np.array(self._embedding)