anchor.diff:        .attr("fill", "white")
         .attr("opacity", 0.75);
   
  -    svg.append("text")
  +    mask.append("text")
         .text("Preview")
         .attr("dy", ".4em")
         .style("text-anchor", "middle")
         .style("font-size", "1.9em");
  +  }
  +  else if (!preview) {
  +    children.remove();
     }
   
   };
  
positive.code:   .style("text-anchor", "middle")
    .attr("font-size", "1.5em")
    .attr("fill", "gray");
  
  var color = d3.scale.category20();
  
  
negative.code:     .remove();
  
    /* ------- PREVIEW (NO DATA) -------*/
    mask = svg.select(".preview");
    children = mask.selectAll("*");
    if (preview && children.empty()) {
      mask.append("rect")
        .attr("x", -width / 2)
        .attr("y", -height / 2)
        .attr("width", width)
  