anchor.diff:    .data(function(d) { return d.contributors; })
     .enter().append("g")
     .attr("class", "contributor")
  -  .attr("transform", "translate(0,"+height+")");
  -
  -//collapse groups
  +  .attr("transform", "translate(0," + height + ")");
  +
  +// Collapse groups
   repo_groups.each(function(d) {
  -  var h = d.score;
  -  d3.select(this).selectAll(".contributor")
  -    .attr("transform", "translate(0,"+y(h)+")");
  +  d3.select(this)
  +    .selectAll(".contributor")
  +    .attr("transform", "translate(0," + y(d.score) + ")");
   });
   
   contributor_groups
  
positive.code:     // breakdown
      t.selectAll(".contributor")
        .attr("transform", function(d) {
          return "translate(0,"+(y(d.y0))+")";
        });
      t.selectAll(".contributor-bar")
        .attr("height", function(d) { return y(d.score); });
  
negative.code: 
  var chart = d3.select("#top-repos")
    .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
  
  var repo_groups = chart.selectAll("g")
    .data(repos)
  