CODEWITHSUNDEEP
pythondictionaryeuclidean-distance
FaCoffee
FaCoffee

Reputation: 7909

Python: how do I create a dict of lists containing the euclidean distances from a point?

Say that I have a regular grid of points with a given set of coordinates, like this:

Node IDs            Coordinates
0   1   2           (0,0)  (1,0)  (2,0)
3   4   5           (0,1)  (1,1)  (2,1)
6   7   8           (0,2)  (1,2)  (2,2)

In my case, the regular grid is a 2D graph generated with NetworkX.

How can I create a dict of lists where the key represents each node ID in the network and the list contains the distances from one specific node to those that are connected to it?

Example: node (0,0) is connected to nodes (1,0) and (0,1). Considering the squared distance to avoid the computational costs of sqrt, the dict I want would feature mydict={0:[1,1],...], since the squared distance from node (0,0) to its connected neighbors is in both cases 1. Each list is therefore as long as there are neighbors to the each node.

I failed to provide some code as I don't understand how to solve the problem. Many thanks to those who will help.

EDIT

This is how the regular network is created:

import networkx as nx
N=3
G=nx.grid_2d_graph(N,N)
pos = dict( (n, n) for n in G.nodes() )
labels = dict( ((i, j), i + (N-1-j) * N ) for i, j in G.nodes() )
nx.relabel_nodes(G,labels,False)
inds=labels.keys()
vals=labels.values()
inds.sort()
vals.sort()
pos2=dict(zip(vals,inds))
nx.draw_networkx(G, pos=pos2, with_labels=False, node_size = 15)

This is how one can get the neighbors of each node:

for node in G.nodes():
        list_of_neigh=G.neighbors(node) #The connected neighbors of node n

And this is how one can access each node in the graph:

G.nodes()

Upvotes: 0

Views: 725

Answers (1)

JulienD
JulienD

Reputation: 7293

Supposing that nodes are tuples (a,b), something like this (not tested)? :

def dist(n1, n2):
    x = n2[0]-n1[0]
    y = n2[1]-n1[1]
    return math.sqrt(x*x + y*y)   # or math.hypot(x, y)

distances = {}
for node in G.nodes():
    list_of_neigh = G.neighbors(node)
    distances[node] = [dist(node, x) for x in list_of_neigh]

Upvotes: 1

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