Undirected Graph: Simple Example

Very simple example how to use undirected graphs

from __future__ import print_function
import nifty.graph
import numpy
import pylab

2D undirected grid graph

numberOfNodes = 5
graph = nifty.graph.undirectedGraph(numberOfNodes)
print("#nodes", graph.numberOfNodes)
print("#edges", graph.numberOfEdges)
print(graph)

Out:

#nodes 5
#edges 0
#Nodes 5 #Edges 0

insert edges

graph.insertEdge(0,1)
graph.insertEdge(0,2)

insert multiple edges at once

uvIds = numpy.array([[0,3],[1,2],[1,4],[1,3],[3,4]])
graph.insertEdges(uvIds)

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 2 e 1
 v 3 e 2
u 1
 v 0 e 0
 v 2 e 3
 v 3 e 5
 v 4 e 4
u 2
 v 0 e 1
 v 1 e 3
u 3
 v 0 e 2
 v 1 e 5
 v 4 e 6
u 4
 v 1 e 4
 v 3 e 6

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: (0, 2)
edge  2 uv: (0, 3)
edge  3 uv: (1, 2)
edge  4 uv: (1, 4)
edge  5 uv: (1, 3)
edge  6 uv: (3, 4)

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

uvIds = graph.uvIds()
print(uvIds)

Out:

[[0 1]
 [0 2]
 [0 3]
 [1 2]
 [1 4]
 [1 3]
 [3 4]]

plot the graph: needs networkx

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

Total running time of the script: ( 0 minutes 0.192 seconds)