D3 streamgraph layer fade function

I recently found this Streamgraph http://bl.ocks.org/1963983:

I am trying to implement the fade function in that example into my own streamgraph but am having no success.

Mine is obviously quite a bit less complicated than the one in that example. Any advice or suggestions would be hugely appreciated!

Thanks.

        var customPalette = [
           "#ff7f0e",  "#2ca02c", "#00FFFF", "#d62728", "#9467bd",
          "#8c564b", "#e377c2", "#7f7f7f", "#bcbd22", "#17becf"
        ];

        var format = d3.time.format("%y");

        //creating margins around the graph
        var margin = {top: 20, right: 30, bottom: 30, left: 200},
            width = 1200 - margin.left - margin.right,
            height = 500 - margin.top - margin.bottom;

        //OUTPUT RANGE
        var x = d3.time.scale()
            .range([0, width]);

        //OUTPUT RANGE
        var y = d3.scale.linear()
            .range([height, 0]);

        //assining custom colors to layers
        var colours = d3.scale.ordinal().range(customPalette);

        var xAxis = d3.svg.axis()
            .scale(x)
            .orient("top")
            .ticks(d3.time.years);

        var yAxis = d3.svg.axis()
            .scale(y)
            .orient("left");

        //ctreate stack layout
        var stack = d3.layout.stack()
            .offset("wiggle")
            .order("reverse")
            .values(function(d) { return d.values; })
            .x(function(d) { return d.date; })
            .y(function(d) { return d.amount; });

        //creates array of datya elements for stacked bar graph
        var nest = d3.nest()
            .key(function(d) { return d.age; });

        //create area
        var area = d3.svg.area()
            //adds curviture
            .interpolate("monotone")
            .x(function(d) { return x(d.date); })
            .y0(function(d) { return y(d.y0); })
            .y1(function(d) { return y(d.y0 + d.y); });

        var svg = d3.select("body").append("svg")
            //defines length of x-axis
            .attr("width", width + margin.left + margin.right)
            //defines height of y-axis
            .attr("height", height + margin.top + margin.bottom)
          .append("g")
            .attr("transform", "translate(" + margin.left + "," + margin.top + ")");


        d3.csv("data6.csv", function(data) {
          data.forEach(function(d) {
            // Convert strings to numbers
            d.date = format.parse(d.date);
            d.amount = +d.amount;
          });

          //returns an array of objects with a key feild (0-20yrs....)
          //and a value array which contains associated records
          var layers = stack(nest.entries(data));

          //.extent() returns min and max values of argument
          x.domain(d3.extent(data, function(d) { return d.date; }));
          //
          y.domain([0, d3.max(data, function(d) { return d.y0 + d.y; })]);

          svg.selectAll(".layer")
              .data(layers)
            .enter().append("path")
              .attr("class", "layer")
              .attr("d", function(d) { return area(d.values); })
              .style("fill", function(d, i) { return colours(i); });


        svg.append("g")
              .attr("class", "x axis")
              .attr("transform", "translate(0," + 0 + ")")
              .call(xAxis);

        svg.append("g")
              .attr("class", "y axis")
              .call(yAxis);

        });

I finally got it working!! I found this handy code here http://bl.ocks.org/3480186

I cut out the chunk for the fade effect. Very happy.

svg.selectAll(".layer").attr("opacity", 1)
.on("mouseover", function(d, i) {
    svg.selectAll(".layer").transition()
      .duration(500)
      .attr("opacity", function(d, j) {
        return j != i ? 0.2 : 1;
      });
  d3.select(this)
    .classed("hover", true);
})
.on("mouseout", function(d, i) {
  svg.selectAll(".layer")
    .transition()
      .duration(500)
      .attr("opacity", 1);
  d3.select(this)
    .classed("hover", false);
});