anchor.diff:                                  return d3.rgb(color(d.target.index)).darker();
                               })
                               .style("visibility", function(d){
  -                                if (mpTopLevelTerms.indexOf(labels[d.source.index].name) < 0 && mpTopLevelTerms.indexOf(labels[d.target.index].name) < 0) {
  -                                    return "hidden";
  +                                if (mpTopLevelTerms && mpTopLevelTerms.length > 0 ){
  +                                    if (mpTopLevelTerms.indexOf(labels[d.source.index].name) < 0 && mpTopLevelTerms.indexOf(labels[d.target.index].name) < 0) {
  +                                        return "hidden";
  +                                    } else {
  +                                        return "visible";
  +                                    }
                                   } else {
                                       return "visible";
                                   }
  
positive.code:                             })
                              .enter().append("g")
                              .attr("class", "group")
  //                            .on("mouseover",  fade(.02, "visible"))
  //                            .on("mouseout",  fade(.80, "hidden"))
                              .on("click", function(d){
                                  window.open(url + "&phenotype_name=" + labels[d.index].name , "_self" );
                              });
  
negative.code: 
                      // Returns an event handler for fading a given chord group.
                      // Display parameter for the group hovering over
                      function fade(opacity) {
                          return function (d, i) {
                              // hide other chords on mose over
                              svg.selectAll("path.chord")
                                      .filter(function (d) {
                                          return d.source.index != i && d.target.index != i;
                                      })
                                      .transition()
                                      .style("stroke-opacity", opacity)
                                      .style("fill-opacity", opacity);
  
                          };
                      }
                  }
  