Draw graph with fixed-positioned edges

Question

I am trying to use NetworkX for Python and it was good so far, but I am stuck with drawing.

My data is actually a list of crossroads in the city. Nodes are the crossroads with X,Y (Latitude, Longitude) and edges should be the roads. So far so simple.

So I managed to draw my little city with fixed positions:

    G = nx.Graph()
    for node in nodes:
      attributes = dict(node.items())
      G.add_node(attributes.pop('id'))
      G.node[node.get('id')]['pos'] = attributes.values()

    pos = nx.get_node_attributes(G, 'pos')
    nx.draw(G,pos)
    plt.show()

It looks like this: A map without edges

Exactly like I want it to, but I need to add the edges. So if I add them like:

    G = nx.Graph()
    for node in nodes:
      attributes = dict(node.items())
      G.add_node(attributes.pop('id'))
      G.node[node.get('id')]['pos'] = attributes.values()

    for link in links:
      attributes = dict(link.items())
      G.add_edge(attributes.pop('from'), attributes.pop('to'))

    pos = nx.get_node_attributes(G, 'pos')
    nx.draw(G,pos)
    plt.show()

I get this horrible error:

Traceback (most recent call last):
   File "ms/Main.py", line 28, in <module>
 nx.draw(G,pos)
   File "/usr/local/lib/python2.7/site-packages/networkx/drawing/nx_pylab.py", line 131, in draw
 draw_networkx(G, pos=pos, ax=ax, **kwds)
    File "/usr/local/lib/python2.7/site-packages/networkx/drawing/nx_pylab.py", line 265, in draw_networkx
 edge_collection = draw_networkx_edges(G, pos, **kwds)
    File "/usr/local/lib/python2.7/site-packages/networkx/drawing/nx_pylab.py", line 610, in draw_networkx_edges
 minx = numpy.amin(numpy.ravel(edge_pos[:, :, 0]))
    File "/usr/local/lib/python2.7/site-packages/numpy/core/fromnumeric.py", line 2216, in amin
 out=out, keepdims=keepdims)
    File "/usr/local/lib/python2.7/site-packages/numpy/core/_methods.py", line 29, in _amin
 return umr_minimum(a, axis, None, out, keepdims)
 TypeError: cannot perform reduce with flexible type

If I do not set the fixed positions I am able to draw it no problem, but I quite need the edges to be static. Any advice? Thanks a lot!

Please check `G.order()` right before and right after the `for link in ...` loop — Joel, Jan 08 '15 at 00:03
Not sure if it's what you've expected but before its printing 282 and after it is still 282 :-) — Atais, Jan 08 '15 at 00:08
hmm... that rules out my guess for what the problem was (thought that networkx was maybe treating the end points of the edges as different objects from the nodes you had added). — Joel, Jan 08 '15 at 00:09
alright - put the answer below... I'm curious. I assume `pos` had strings or something non number in it? — Joel, Jan 08 '15 at 00:14

score 0 · Accepted Answer · answered Feb 24 '15 at 09:56

The X,Y data is not being treated as numbers.

You can fix it with this:

 xy = attributes.values()
 G.add_node(attributes.pop('id'), dict([('pos', (float(xy[0]),float(xy[1])) )]))

Note: this answer was edited into the question by the OP. I've moved it down here into the answers section and made it a community wiki so I won't earn any rep for it.

Draw graph with fixed-positioned edges

1 Answers1