/ ///////////////////////////////////////////////////////////////////////////////// Cycle functions portion of code to detect circular links based on Colin Fergus' bl.ock https://gist.github.com/cfergus/3956043 Identify circles in the link objects
function identifyCircles (graph, id, sortNodes) {

    var circularLinkID = 0

    if (sortNodes === null) {

      // Building adjacency graph
      var adjList = []
      for (var i = 0; i < graph.links.length; i++) {
          var link = graph.links[i];
          var source = link.source.index;
          var target = link.target.index;
          if (!adjList[source]) adjList[source] = []
          if (!adjList[target]) adjList[target] = []

          // Add links if not already in set
          if (adjList[source].indexOf(target) === -1) adjList[source].push(target);
      }

      // Find all elementary circuits
      var cycles = findCircuits(adjList);

      // Sort by circuits length
      cycles.sort(function(a, b){
          return a.length - b.length;
      });

      // Make one link circular for each elementary circuit
      var circularLinks = {};
      for (i = 0; i < cycles.length; i++) {
          var cycle = cycles[i];
          var closed = false;
          for (var j = 0; j < cycle.length - 1; j++){
              if (!circularLinks[cycle[j]]) circularLinks[cycle[j]] = {};

              // Check if there is already a circular link in the circuit
              if (circularLinks[cycle[j]] && circularLinks[cycle[j]][cycle[j + 1]]) {
                closed = true;
                break;
              }
          }

          if (!closed) {
            // If not closed, make the last link the circular one
            var last = cycle.slice(-2);
            circularLinks[last[0]][last[1]] = true
          }
      }

      graph.links.forEach(function (link) {
        var target = link.target.index;
        var source = link.source.index;
        // If self-linking or a back-edge
        if (target === source || (circularLinks[source] && circularLinks[source][target])) {
          link.circular = true
          link.circularLinkID = circularLinkID
          circularLinkID = circularLinkID + 1
        } else {
          link.circular = false
        }
      })

    } else {
      graph.links.forEach(function(link) {
        if (link.source[sortNodes] < link.target[sortNodes]) {
          link.circular = false
        } else {
          link.circular = true
          link.circularLinkID = circularLinkID
          circularLinkID = circularLinkID + 1
        }
      })

    }
  }