Color a particular node in Networkx and Graphviz

Question

I am writing a program to plot a graph from a distance matrix. It is working fine. Now I want a certain node and a certain edge to be of a particular color of my choice. How do I do that?

The program is in Python and uses Networkx and Graphviz

import networkx as nx import numpy as np import pickle from random import randint p_file = open('pickles/distance') Dist = pickle.load(p_file) p_file.close() p_file = open('pickles/names') Names = pickle.load(p_file) p_file.close() dt = [('len', float)] A = np.array(Dist)*5 A = A.view(dt) G = nx.from_numpy_matrix(A) G = nx.relabel_nodes(G, dict(zip(range(len(G.nodes())),Names))) G = nx.to_agraph(G) G.node_attr.update(ndcolor="red", node="DC", style="filled") G.edge_attr.update(color="none") G.draw('P1.png', format='png', prog='neato')

Aric · Accepted Answer · 2019-11-12 18:25:28Z

Since you are using Graphviz to do the drawing you need to use the attributes that Graphviz understands. See https://graphviz.gitlab.io/_pages/doc/info/attrs.html

import networkx as nx from networkx.drawing.nx_agraph import to_agraph G = nx.Graph() G.add_node(1,color='red',style='filled',fillcolor='blue',shape='square') G.add_node(2,color='blue',style='filled') G.add_edge(1,2,color='green') G.nodes[2]['shape']='circle' G.nodes[2]['fillcolor']='red' A = to_agraph(G) A.layout() A.draw('color.png') print(A.to_string())

Gives

strict graph { graph [bb="0,0,107.21,46.639"]; node [label="\N"]; 1 [color=red, fillcolor=blue, height=0.5, pos="18,28.639", shape=square, style=filled, width=0.5]; 2 [color=blue, fillcolor=red, height=0.5, pos="89.21,18", shape=circle, style=filled, width=0.5]; 1 -- 2 [color=green, pos="36.338,25.899 47.053,24.298 60.519,22.286 71.18,20.694"]; }

enter image description here

As you can see in my code, I am adding nodes and edges from the distance matrix. The method you have mentioned cannot be applied in this case. Do you know any other method?
You can add the attributes after you create the graph G. Use G.node[nodename]['color']='red', etc.
Oh it worked! Thank you Aric. Can you pls add this to the answer so that it'll help others too.
Does this code work in 2019? I get AttributeError: 'module' object has no attribute 'to_agraph'. See stackoverflow.com/questions/35279733/… How to make the above work?

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