how to add subgraph with (new nodes, new edges) to an existed graph in python


I’m trying to add new nodes (red dots) with new edges (green lines) to be places diagonaly
new color and positions to this grid graph Graph

import networkx as nx
import matplotlib.pyplot as plt

G = nx.grid_graph(dim=[5, 5])

nodes = list(G.nodes)
edges = list(G.edges)

p = []
for i in range(0, 5):
    for j in range(0, 5):
        p.append([i, j])

for i in range(0, len(nodes)):
    G.nodes[nodes[i]]['pos'] = p[i]

pos = {}
for i in range(0, len(nodes)):
    pos[nodes[i]] = p[i]

nx.draw(G, pos)
Asked By: user4556432



Sorry, your question is not clear for me, but you can create list of edges and then use G.add_edges_from() to add nodes & edges to your initial graph

Probably you should define algorithm to find coordinates / labels of new nodes, then construct edges and add by G.add_edges_from()

G = nx.grid_graph(dim=[5, 5])

new_edges = [((0.5, 1.5), (0.5, 2.5)),
             ((0.5, 1.5), (0, 2)),
             ((0.5, 2.5), (0, 2))]


nx.draw(G, pos={n:n for n in G.nodes()})

enter image description here


I modified code:

  • nodes are renamed and have ‘coord’ and ‘color’ attributes
  • graph are drawn wrt color of node

Probably there is a better way to solve this problem cause code looks massive)

G = nx.grid_graph(dim=[5, 5])

# rename nodes & set coord and color (0 - blue, 1 - red) attributes to nodes
nx.set_node_attributes(G, {n: {"coord": n, "color": 0} for n in G.nodes()})
nx.relabel_nodes(G, mapping={coord:label
                             for label,coord in zip(range(len(G)), G.nodes())}, copy=False)

# we are GIVEN list nodes & edges to add
new_nodes = [(label, {'coord': coord, 'color': 1})
             for label, coord in zip([26, 27], [(0.5, 1.5), (0.5, 2.5)])]
new_edges = [(2, 26), (2, 27), (26, 27)]


color_map = {0: '#7d99f5', 1: '#f57d7d'}
nx.draw_networkx(G, pos={n:G.nodes[n]['coord'] for n in G.nodes()},
                             for n in G.nodes(data=True)])

enter image description here

Answered By: glebcom
Categories: questions Tags: , ,
Answers are sorted by their score. The answer accepted by the question owner as the best is marked with
at the top-right corner.