= y(idToNode[d.source].name)    // X position of start node on the X axis
      end = y(idToNode[d.target].name)      // X position of end node
      return ['M', 50, start,    // the arc starts at the coordinate x=start, y=height-30 (where the starting node is)
        'A',                            // This means we're gonna build an elliptical arc
        (start - end)/2*4, ',',    // Next 2 lines are the coordinates of the inflexion point. Height of this point is proportional with start - end distance
 