使用 matplotlib 绘制随机生成的图形

Question

I found this script and modified it to color a graph that I randomly generate. I now want to draw that graph with the color that the script assigns to the vertices. I managed to draw the graph with networkx which uses matplotlib but I don't know how to draw it using the colors assigned by the script. This is my script:

import networkx as nx 
import matplotlib.pyplot as plt
from random import sample
from random import randrange
# Python3 program to implement greedy
# algorithm for graph coloring

def addEdge(adj, v, w):
    
    adj[v].append(w)
    
    # Note: the graph is undirected
    adj[w].append(v)
    return adj

# Assigns colors (starting from 0) to all
# vertices and prints the assignment of colors
def greedyColoring(adj, V):
    
    result = [-1] * V

    # Assign the first color to first vertex
    result[0] = 0;


    # A temporary array to store the available colors.
    # True value of available[cr] would mean that the
    # color cr is assigned to one of its adjacent vertices
    available = [False] * V

    # Assign colors to remaining V-1 vertices
    for u in range(1, V):
        
        # Process all adjacent vertices and
        # flag their colors as unavailable
        for i in adj[u]:
            if (result[i] != -1):
                available[result[i]] = True

        # Find the first available color
        cr = 0
        while cr < V:
            if (available[cr] == False):
                break
            
            cr += 1
            
        # Assign the found color
        result[u] = cr

        # Reset the values back to false
        # for the next iteration
        for i in adj[u]:
            if (result[i] != -1):
                available[result[i]] = False

    # Print the result
    for u in range(V):
        print("Vertex", u, " ---> Color", result[u])


     
q = [0,1,2,3,4]
d = {i: sample([j for j in q if i != j], randrange(1, len(q) - 1))
     for i in q}
print(d)
greedyColoring([node for node in d.values()], 5)

options = {
    'node_color': 'red',
    'node_size': 4,
    'width': .1,
}


G = nx.Graph()
def passacolorsNx():
    for k in d:
        for j in d[k]:
            G.add_node(j)
            G.add_edges_from([(k, j)])
passcolorsNx()

subax1 = plt.subplot(121)
nx.draw(G, **options)
plt.show()

As you can see, to pass the randomly generated graph to networkx I created the function

Passcolorsnx()

Answer 1

You can use a node-color map. Here's the modified code from the snippet you posted (note that now you need to return the result to store the colors). Fixed the typo in passcolorsNx . You can modify result to contain actual color names if you want to override the default colorscheme.

import networkx as nx 
import matplotlib.pyplot as plt
from random import sample
from random import randrange
# Python3 program to implement greedy
# algorithm for graph coloring

def addEdge(adj, v, w):
    
    adj[v].append(w)
    
    # Note: the graph is undirected
    adj[w].append(v)
    return adj

# Assigns colors (starting from 0) to all
# vertices and prints the assignment of colors
def greedyColoring(adj, V):
    
    result = [-1] * V

    # Assign the first color to first vertex
    result[0] = 0;


    # A temporary array to store the available colors.
    # True value of available[cr] would mean that the
    # color cr is assigned to one of its adjacent vertices
    available = [False] * V

    # Assign colors to remaining V-1 vertices
    for u in range(1, V):
        
        # Process all adjacent vertices and
        # flag their colors as unavailable
        for i in adj[u]:
            if (result[i] != -1):
                available[result[i]] = True

        # Find the first available color
        cr = 0
        while cr < V:
            if (available[cr] == False):
                break
            
            cr += 1
            
        # Assign the found color
        result[u] = cr

        # Reset the values back to false
        # for the next iteration
        for i in adj[u]:
            if (result[i] != -1):
                available[result[i]] = False

    # Print the result
    for u in range(V):
        print("Vertex", u, " ---> Color", result[u])
    return result


     
q = [0,1,2,3,4]
d = {i: sample([j for j in q if i != j], randrange(1, len(q) - 1))
     for i in q}
print(d)
result = greedyColoring([node for node in d.values()], 5)

options = {
    'node_color': result,
    'node_size': 4,
    'width': .1,
}


G = nx.Graph()
def passcolorsNx():
    for k in d:
        G.add_node(k)
        for j in d[k]:
            G.add_edge(k, j)
passcolorsNx()

subax1 = plt.subplot(121)
nx.draw(G, **options)
plt.show()