from_numpy_array

from_numpy_array(A, parallel_edges=False, create_using=None, edge_attr='weight')

Returns a graph from a 2D NumPy array.

The 2D NumPy array is interpreted as an adjacency matrix for the graph.

Parameters:

Aa 2D numpy.ndarray

An adjacency matrix representation of a graph

parallel_edgesBoolean

If this is True, create_using is a multigraph, and A is an integer array, then entry (i, j) in the array is interpreted as the number of parallel edges joining vertices i and j in the graph. If it is False, then the entries in the array are interpreted as the weight of a single edge joining the vertices.

create_usingNetworkX graph constructor, optional (default=nx.Graph)

Graph type to create. If graph instance, then cleared before populated.

edge_attrString, optional (default=”weight”)

The attribute to which the array values are assigned on each edge. If it is None, edge attributes will not be assigned.

See also

to_numpy_array

Notes

For directed graphs, explicitly mention create_using=nx.DiGraph, and entry i,j of A corresponds to an edge from i to j.

If create_using is networkx.MultiGraph or networkx.MultiDiGraph, parallel_edges is True, and the entries of A are of type int, then this function returns a multigraph (of the same type as create_using) with parallel edges.

If create_using indicates an undirected multigraph, then only the edges indicated by the upper triangle of the array A will be added to the graph.

If edge_attr is Falsy (False or None), edge attributes will not be assigned, and the array data will be treated like a binary mask of edge presence or absence. Otherwise, the attributes will be assigned as follows:

If the NumPy array has a single data type for each array entry it will be converted to an appropriate Python data type.

If the NumPy array has a user-specified compound data type the names of the data fields will be used as attribute keys in the resulting NetworkX graph.

Examples

Simple integer weights on edges:

>>> import numpy as np
>>> A = np.array([[1, 1], [2, 1]])
>>> G = nx.from_numpy_array(A)
>>> G.edges(data=True)
EdgeDataView([(0, 0, {'weight': 1}), (0, 1, {'weight': 2}), (1, 1, {'weight': 1})])

If create_using indicates a multigraph and the array has only integer entries and parallel_edges is False, then the entries will be treated as weights for edges joining the nodes (without creating parallel edges):

>>> A = np.array([[1, 1], [1, 2]])
>>> G = nx.from_numpy_array(A, create_using=nx.MultiGraph)
>>> G[1][1]
AtlasView({0: {'weight': 2}})

If create_using indicates a multigraph and the array has only integer entries and parallel_edges is True, then the entries will be treated as the number of parallel edges joining those two vertices:

>>> A = np.array([[1, 1], [1, 2]])
>>> temp = nx.MultiGraph()
>>> G = nx.from_numpy_array(A, parallel_edges=True, create_using=temp)
>>> G[1][1]
AtlasView({0: {'weight': 1}, 1: {'weight': 1}})

User defined compound data type on edges:

>>> dt = [("weight", float), ("cost", int)]
>>> A = np.array([[(1.0, 2)]], dtype=dt)
>>> G = nx.from_numpy_array(A)
>>> G.edges()
EdgeView([(0, 0)])
>>> G[0][0]["cost"]
2
>>> G[0][0]["weight"]
1.0