convert a simple matrix to incidence matrix with python

Question

i want to make graph network from incidence Matrix, but i don't have an incidence Matrix, i have just a simple Matrix.so my question is: how to convert a simple Matrix to a incidence Matrix to draw a graph network with python?

Answer 1

Both matrices are adjacency matrices. The most important thing is to know that they are different datatypes:

import pandas as pd
import numpy as np

adjacency = [[0,0,-1,0,0], [1,1,-1,-1,0], [1,-1,0,0,0], [1,0,0,-1,0], [1,0,1,-1,1]]
df = pd.DataFrame(adjacency, columns = ['A','B','C','D','E'], index = ['A','B','C','D','E'])

This results in different methods of handling incidencies as well as different structure of graph:

As you can note easily, first method uses automatic assignment of node labels to indices 0, 1, 2, 3, 4.

Another surprising facts: you don't need to collect weights manually. They are stored in weight attribute of edges.

Usage:

You can access edge attributes with nx.get_edge_attributes(G, 'weight'). This is my simplified version of diagram structure:

G = nx.from_pandas_adjacency(df)
pos = nx.circular_layout(G)
nx.draw(G, pos, with_labels=True, bbox = dict(fc="lightgreen", ec="black", boxstyle="circle", lw=3),
    width=2, arrowsize=30)
nx.draw_networkx_edge_labels(G, pos, edge_labels = nx.get_edge_attributes(G, 'weight'))
plt.show()