d3.js - 在 y 轴 d3 上添加一条线

Question

我使用 d3.js 创建了一个条形图，但我需要在 y 轴 80 处穿过图表的黑色实线来指示“最大阈值”

我已经弄清楚如何在底部画一条线，但我需要它始终显示在图表上的值 80 处。有办法做到这一点吗？

var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.scale.ordinal()
    .rangeRoundBands([0, width], .1);

var y = d3.scale.linear()
    .range([height, 0])
    .domain([0,1000]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .ticks(10);


var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.tsv("data.tsv", type, function(error, data) {
  x.domain(data.map(function(d) { return d.name; }));
  y.domain([0, d3.max(data, function(d) { return d.risk; })]);

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

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

  var div = d3.select("body").append("div")
    .attr("class", "tooltip")
    .style("opacity", 0);
  svg.selectAll(".bar")
      .data(data)
    .enter().append("rect")
      .attr("class", "bar")
      .attr("x", function(d) { return x(d.name); })
      .attr("width", x.rangeBand())
      .attr("y", function(d) { console.log(d); return y(d.risk); })
      .attr("height", function(d) { return height - y(d.risk); })
      .style("fill", function(d) {            // <== Add these
            if (d.risk >= 80) {return "#e74c3c"}  // <== Add these
            else    { return "#3498db" }          // <== Add these
        ;})
      .on("mouseover", function(d) {
        // debugger
        d3.select(this).transition().style({opacity:'0.6'});
         console.log(d,this.x);
            div.transition()
                .duration(200)
                .style("opacity", .9);
            div .html(d.risk)
                .style("left", (this.x.baseVal.value + (this.width.baseVal.value/2) + 15) + "px")
                .style("top", (this.y.baseVal.value + (this.height.baseVal.value/2)) + "px");
            })
        .on("mouseout", function(d) {
            div.transition()
                .duration(500)
                .style("opacity", 0);
            d3.select(this).transition().style({opacity:'1'});
        });

      var median = d3.median(svg.selectAll('.bar').data(),
        function(d) { return d.risk; });

      var median = svg.append("line")
                         .attr("x1", 0)
                         .attr("y1", (height/10)*0.8)
                         .attr("x2", width)
                         .attr("y2", (height/10)*0.8)
                         .attr("stroke-width", 2)
                         .attr("stroke", "black");

});

Answer 1

您已经构建了一个比例函数y，它将输入比例上的值转换为图表高度输出范围。当您计算在哪里绘制每个条形的顶部时，您可以使用它。您可以在绘制阈值线时再次使用此函数:

// not clear if you meant 80 as 80% or as literal value 80 on your input scale
var threshold = 80;

var median = svg.append("line")
                     .attr("x1", 0)
                     .attr("y1", y(threshold))
                     .attr("x2", width)
                     .attr("y2", y(threshold))
                     .attr("stroke-width", 2)
                     .attr("stroke", "black");