lor = colors[i];
          clusterOptionsByData = {
              joinCondition: function (childOptions) {
                  return childOptions.color.background == color; // the color is fully defined in the node.
              },
              processProperties: function (clusterOptions, childNodes, childEdges) {
                  var totalMass = 0;
                  for (var i = 0; i < childNodes.length; i++) {
                      totalMass += childNodes[i].mass;
                  }
                  c