anchor.diff:  
     svg.append("g")
         .attr("class", "y axis")
  -      .call(yAxis)
  +      .call(yAxisWeight)
       .append("text")
         .attr("transform", "rotate(-90)")
         .attr("y", 6)
  
positive.code:       .style("text-anchor", "end")
        .text("Weight");
  
    svg.append("path")
        .datum(data)
        .attr("class", "line")
        .attr("d", line);
  });
  
  </script>
  
negative.code:   });
  
    x.domain(d3.extent(data, function(d) { return d.measurementDate; }));
    yWeight.domain(d3.extent(data, function(d) { return d.weight; }));
    yBf.domain(d3.extent(data, function(d) { return d.bodyFat; }));
  
  
    svg.append("g")
        .attr("class", "x axis")
  