How to create a connected 2D grid graph?

Question

I have a 2-dimensional array that represents a grid. The (numpy) array is as follows:

dx_grid =[[ "A", "B", "C"],
          [ "L", "M", "N"],
          [ "X", "Y", "Z"]]

I want to convert that into the following:

I know that grid_2d_graph can connect 4 adjacent nodes. For example, it would connect node M to B, L, N and Y BUT NOT to A, C, X, Z. How would I create such a graph using networkx in python?

Answer 1

Something like this should work:

import networkx as nx

dx_grid =[[ "A", "B", "C"],
          [ "L", "M", "N"],
          [ "X", "Y", "Z"]]
r, c = len(dx_grid), len(dx_grid[0])

g = nx.Graph()

# add nodes 
for i in range(r):
    for j in range(c):
        g.add_node(dx_grid[i][j], pos=(j,r-i))

# add edges
# for all nodes
for i in range(r):
    for j in range(c):
        # connect all neighbors
        for k in range(-1,2):
            for l in range(-1,2):
                # check if neighbor node index is valid 
                if i+k >= 0 and i+k < r and j+l >= 0 and j+l < c:
                    if k == 0 and l == 0: continue # avoid self-loops
                    g.add_edge(dx_grid[i][j], dx_grid[i+k][j+l]) # connect with neighbor node
# get positions
pos = nx.get_node_attributes(g,'pos')
# draw network with nodes at given positions
plt.figure(figsize=(6,6))
nx.draw(g, 
        pos=pos, 
        node_color='lightblue', 
        with_labels=True,
        node_size=600)