凹痕js线和气泡图重叠

Question

我有一些气泡和折线图在图表上的几个点重叠。然而，重叠隐藏了另一个点，使视觉混乱。任何人都可以修复这个jsfiddle所以在悬停在重叠点上显示工具提示两个点值。这是jsfiddle：http://jsfiddle.net/d54vY/

var svg = dimple.newSvg("#chartContainer", 590, 400);

    // The default data set for these examples has regular times
    // and the point of this demo is to show the time axis
    // functionality, therefore a small bespoke data set is used.
    data = [
      { "Shift":"2012","Date":"12 Jul 2010 10:00","Value":1000 },
      { "Shift":"2012","Date":"20 Jul 2010 10:20","Value":1200 },
      { "Shift":"2012","Date":"1 Aug 2010 10:00","Value":1600 },
      { "Shift":"2012","Date":"8 Aug 2010 10:00","Value":1700 },
      { "Shift":"2013","Date":"12 Jul 2010 10:00","Value":2400 },
      { "Shift":"2013","Date":"20 Jul 2010 10:00","Value":2000 },
      { "Shift":"2013","Date":"1 Aug 2010 10:00","Value":1600 },
      { "Shift":"2013","Date":"8 Aug 2010 10:00","Value":1700 },
    ];

    // Create Separate Date and Time, this allows us to draw them
    // on separate axes.  Despite the time axis only displaying
    // the time portion, the whole date is used so they need to
    // have the same date allocated
    data.forEach(function (d) {
        d["Day"] = d["Date"].substring(0, d["Date"].length - 6);
        d["Time of Day"] =
            "2000-01-01 " + d["Date"].substring(d["Date"].length - 5);
    }, this);

    // Create the chart as usual
    var myChart = new dimple.chart(svg, data);
    myChart.setBounds(70, 40, 490, 320)

    // Add the x axis reading dates in the format 01 Jan 2012
    // and displaying them 01 Jan
    var x = myChart.addTimeAxis("x", "Day", "%d %b %Y", "%d %b");

    // Add the y axis reading dates and times but only outputting
    // times.  
    //var y = myChart.addTimeAxis("y", "Time of Day",
    //    "%Y-%m-%d %H:%M", "%H:%M");

    var y = myChart.addMeasureAxis("y", "Value");
    // Size the bubbles by volume
    var z = myChart.addMeasureAxis("z", "Value");

    // Setting min and max dates requires them to be set
    // as actual javascript date objects
    x.overrideMin = new Date("2010-06-20");
    x.overrideMax = new Date("2011-01-02");
    //y.overrideMin = new Date("01/01/2000 9:00 am");
    //y.overrideMax = new Date("01/01/2000 6:00 pm");

    // Show a label for every 4 weeks.
    x.timePeriod = d3.time.weeks;
    x.timeInterval = 4;

    // Control bubble sizes by setting the max and min values    
    z.overrideMin = 900;
    z.overrideMax = 3000;

    // Add the bubble series for shift values first so that it is
    // drawn behind the lines
    myChart.addSeries("Shift", dimple.plot.bubble);

    // Add the line series on top of the bubbles.  The bubbles
    // and line points will naturally fall in the same places
    var s = myChart.addSeries("Shift", dimple.plot.line);

    // Add line markers to the line because it looks nice
    s.lineMarkers = true;

    // Show a legend
    myChart.addLegend(180, 10, 360, 20, "right");

    // Draw everything
    myChart.draw();