[FIXED] Highlight a node in draw_networkx visualisation without changing node colour

Issue

I am using NetworkX to visualise a large graph with > 1000 nodes. As part of that visualisation, I wanted to be able to highlight certain nodes.

I have seen this question and am aware that NetworkX will allow you to highlight a node by changing the node colour like this:

import networkx as nx
import matplotlib.pyplot as plt
edges = [['A','B'], ['A','C'], ['A','D'], ['B','E'], ['B','F'], ['D','G'],['D','H'],['F','I'],['G','J'],['A','K']]
G = nx.Graph()
G.add_edges_from(edges)

colours = ['blue']*5 + ['red'] + ['blue']*5
nx.draw_networkx(G, font_size=16, node_color=colours)
plt.show()

But, with a large number of nodes, I have had to reduce the node size significantly, otherwise it just appears as a blurry cloud of overlapping nodes, so changing the node colour isn't effective.

What I would ideally like to do is change the label font colour to, say, red for the text label of chosen nodes.Unlike node_color, however, NetworkX only seems to offer a global argument font_color to change the colour for all node labels and it won't accept, e.g. font_color=colours.

If there any way through NetworkX or Matplotlib to either change the font colour for a specific node/group of nodes, or to add any sort of call-out, or any other way to highlight certain nodes without relying on changing node_color?

Solution

You can draw a subgraph on top of your original graph:

# generate node positions:
pos = nx.spring_layout(G)

# draw graph
nx.draw_networkx(G, pos=pos, font_size=16, node_color='blue', font_color='white')

# draw subgraph for highlights
nx.draw_networkx(G.subgraph('F'), pos=pos, font_size=16, node_color='red', font_color='green')

Answered By - warped