Undirected Grid Graph

2D and 3D undirected with simple neighborhood (4-neighborhood in 2D, 6-neighborhood in 3D)

from __future__ import print_function
import nifty.graph
import pylab

2D undirected grid graph

shape = [3, 3]
graph = nifty.graph.undirectedGridGraph(shape)
print("#nodes", graph.numberOfNodes)
print("#edges", graph.numberOfEdges)
print(graph)

Out:

#nodes 9
#edges 12
#Nodes 9 #Edges 12

iterate over nodes and the adjacency of each node

for node in graph.nodes():
    print("u",node)
    for v,e in graph.nodeAdjacency(node):
        print(" v",v,"e",e)

Out:

u 0
 v 1 e 0
 v 3 e 6
u 1
 v 0 e 0
 v 2 e 1
 v 4 e 7
u 2
 v 1 e 1
 v 5 e 8
u 3
 v 0 e 6
 v 4 e 2
 v 6 e 9
u 4
 v 1 e 7
 v 3 e 2
 v 5 e 3
 v 7 e 10
u 5
 v 2 e 8
 v 4 e 3
 v 8 e 11
u 6
 v 3 e 9
 v 7 e 4
u 7
 v 4 e 10
 v 6 e 4
 v 8 e 5
u 8
 v 5 e 11
 v 7 e 5

iterate over edges and print the endpoints

for edge in graph.edges():
    print("edge ",edge, "uv:", graph.uv(edge))

Out:

edge  0 uv: (0, 1)
edge  1 uv: (1, 2)
edge  2 uv: (3, 4)
edge  3 uv: (4, 5)
edge  4 uv: (6, 7)
edge  5 uv: (7, 8)
edge  6 uv: (0, 3)
edge  7 uv: (1, 4)
edge  8 uv: (2, 5)
edge  9 uv: (3, 6)
edge  10 uv: (4, 7)
edge  11 uv: (5, 8)

get the uv-ids /endpoints for all edges simultaneous as a numpy array

uvIds = graph.uvIds()
print(uvIds)

Out:

[[0 1]
 [1 2]
 [3 4]
 [4 5]
 [6 7]
 [7 8]
 [0 3]
 [1 4]
 [2 5]
 [3 6]
 [4 7]
 [5 8]]

get the coordinates of a node

for node in graph.nodes():
    print("node",node,"coordiante",graph.nodeToCoordinate(node))

Out:

node 0 coordiante [0, 0]
node 1 coordiante [0, 1]
node 2 coordiante [0, 2]
node 3 coordiante [1, 0]
node 4 coordiante [1, 1]
node 5 coordiante [1, 2]
node 6 coordiante [2, 0]
node 7 coordiante [2, 1]
node 8 coordiante [2, 2]

get the node of a coordinate

for x0 in range(shape[0]):
    for x1 in range(shape[1]):
        print("coordiante",[x0,x1],"node",graph.coordianteToNode([x0,x1]))

Out:

coordiante [0, 0] node 0
coordiante [0, 1] node 1
coordiante [0, 2] node 2
coordiante [1, 0] node 3
coordiante [1, 1] node 4
coordiante [1, 2] node 5
coordiante [2, 0] node 6
coordiante [2, 1] node 7
coordiante [2, 2] node 8

plot the graph: needs networkx

nifty.graph.drawGraph(graph)
pylab.show()

Total running time of the script: ( 0 minutes 0.047 seconds)