如何在nvd3.js堆积区域图表中添加"平均"线？

Question

我有一个使用NVD3.js的堆积区域图表:在这里工作jsfiddle

var volumeData = [{"key":"Hit","values":[[1.3781628E12,12],[1.3782492E12,9],[1.3783356E12,9],[1.378422E12,4],[1.3785084E12,2],[1.3785948E12,3],[1.3786812E12,6],[1.3787676E12,5],[1.378854E12,1],[1.3789404E12,5],[1.3790268E12,1],[1.3791132E12,3],[1.3791996E12,0],[1.379286E12,2],[1.3793724E12,0]]},{"key":"Miss","values":[[1.3781628E12,3],[1.3782492E12,3],[1.3783356E12,1],[1.378422E12,12],[1.3785084E12,4],[1.3785948E12,7],[1.3786812E12,10],[1.3787676E12,13],[1.378854E12,14],[1.3789404E12,8],[1.3790268E12,5],[1.3791132E12,2],[1.3791996E12,3],[1.379286E12,11],[1.3793724E12,6]]}];


(function(data){
    var colors = d3.scale.category20();
    keyColor = function(d, i) {return colors(d.key)};

    var chart;
    nv.addGraph(function() {
        chart = nv.models.stackedAreaChart()
        .x(function(d) { return d[0] })
        .y(function(d) { return d[1] })
        .color(keyColor);

        chart.xAxis.tickFormat(function(d) { return d3.time.format('%x')(new Date(d)) });

        chart.yAxis.tickFormat(d3.format('d'));

        d3.select('#graph svg')
        .datum(data)
        .transition().duration(0)
        .call(chart);

        //nv.utils.windowResize(chart.update);

        return chart;
    });
})(volumeData);

我想做的是在可见x范围内为每个系列添加"平均"线.我可以毫不费力地计算每个系列的平均值,我只是不知道如何让这条线显示在图表上.

是否可以使用nvd3.js,或者我必须下载到d3才能执行此操作？

Answer 1

另外两个选项:
1.快速但有点hacky,通过为每个x值设置相同的y值,为每条平均线在数据中创建另一条线.虽然每个x刻度将具有相同平均值的工具提示,但您将得到一条直线.
2.从平均值在yAxis上的点绘制整个图表的固定线:

//margin from chart declaration
var margin = { top: 30, right: 60, bottom: 60, left: 100 };
//calculate the yScale
var yScale = chart.yAxis.scale();
//call generic function...since you'll want this on potentially multiple types of charts
drawFixedLineAndText(chartID, 960, margin, <your average value goes here>, yScale, <your average label text goes here>);

function drawFixedLineAndText(chartName, width, margin, yValue, yValueScale, text) {
var svg = d3.select("#" + chartName + " svg");
svg.append("line")
    .style("stroke", "#FF7F0E")
    .style("stroke-width", "2.5px")
    .attr("x1", margin.left)
    .attr("y1", yValueScale(yValue) + margin.top)
    .attr("x2", width - margin.right)
  .attr("y2", yValueScale(yValue) + margin.top);


//add text to fixed line
d3.select("#" + chartName + " svg")
    .append("text")
    .attr("x", width - margin.right / 2)
    .attr("y", yValueScale(yValue) + margin.top)
    .attr("text-anchor", "middle")
    .text(text);
//end fixed line
}