title: Interactively fixing a node in a directed force graph
body: <p>I am currently working with a rather plain, but large force directed graph and I want my users to be able organize the graph however they see fit at the time. To do this, I want to allow them to interactively fix the position of the node. The method of locking the node is up to me; I'm thinking either double clicking the node or pressing a key while mousing over/grabbing the node.</p>
  
  <p>I am unsure of how to do this and cannot find any examples and would greatly appreciate some assistance.</p>
  
  <p>Thank you very much.</p>