title: Networkx: node size must correlate to dimension
body: <p>I'm trying to use networkx to draw circles at particular positions. Each of the circle I want to draw has a set of coordinates, and a radius.</p>
  
  <p>I can set the coordinates easily:</p>
  
  <pre><code>import networkx as nx
  import matplotlib.pyplot as plt
  
  positions = [(0, 0), (36.439507534009273, 0.0),
               (36.439507534009273, -36.439507534009273),
               (36.439507534009273, -72.879015068018546),
               (0.0, -72.879015068018546),
               (2.231276313201516e-15, -109.31852260202781),
               (4.4625526264030319e-15, -145.75803013603709),
               (36.43950753400928, -145.75803013603709),
               (36.43950753400928, -182.19753767004639)]
  
  G = nx.Graph()
  
  pos = dict()
  
  for i, couple in enumerate(positions):
      G.add_node(i)
      print(couple)
      pos[i] = couple
  
  
  print(G.number_of_nodes())
  
  fig = plt.figure(1)
  
  nodes = nx.draw_networkx_nodes(G, pos)
  
  nx.draw_networkx_edges(G, pos)
  
  plt.axis('equal')
  plt.savefig('drawing.png', bbox_inches='tight', dpi=400)
  plt.clf()
  </code></pre>
  
  <p>But I can't set the radius properly. The positions in my example are in millimetres, and the radii of my circles will be as well.</p>
  
  <p><a href="https://i.stack.imgur.com/qEFjp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qEFjp.png" alt="enter image description here"></a></p>
  
  <p>I can set the "size of the nodes" with <code>node_size</code>, but I don't think I can correlate <code>node_size</code> to my radii. For example, the default for <code>node_size</code> is 300, and I don't know what it corresponds to.</p>
  
  <p>If I have a circle at position let's say (20, 20), and the radius is 20, I should have a circle ranging from 0 to 40 (in x).</p>
  
  <p>How can I achieve that with networkx ?</p>