title: Sum up shortest paths in a weighted network
body: <p>I have a <code>graph</code> with 340 <code>nodes</code> and 700 <code>links</code>. As for performance indicator of the network, I want to compute the sum of all <code>weighted shortest paths</code> in my network. </p>
  
  <p>I tried the <code>all_shortest_paths</code> command from the <code>igraph</code> package. But my system doesn't have enough RAM to store the resulting matrix. 
  Can someone recommend a <code>package</code> or <code>code</code> which computes the sum of all shortest paths? (So the big matrix is not needed?)
  For <code>unweighted</code> networks is the command <code>mean_distance</code>, which does basically something similar!?</p>