Question

状况：

问题：

我正在尝试使用我管理的D3.js创建热图图表。我现在无法使传奇出现。

为什么没有图例出现？

图例应如下所示：https://codepen.io/freeCodeCamp/full/aNLYPp

CODE：

<script type="text/javascript">  

    // Excellent example from Tom May helped me when I got stuck: http://bl.ocks.org/tjdecke/5558084
    d3.json("https://raw.githubusercontent.com/FreeCodeCamp/ProjectReferenceData/master/global-temperature.json", function(error, json) {
      if (error) {
          return console.warn(error);
      }
      visualizeThe(json);
    });

    function visualizeThe(data) {

        const baseTemperature = data.baseTemperature;
        const tempData = data.monthlyVariance;

        const margin = {
            top: 10,
            right: 85,
            bottom: 65,
            left: 70
        }

        const w = 1250 - margin.left - margin.right;
        const h = 500 - margin.top - margin.bottom;
        const barWidth = Math.ceil(w / tempData.length);
        const legendElementWidth = w/12;


        const colors = ["#5e4fa2", "#3288bd", "#66c2a5", "#abdda4", "#e6f598", "#ffffbf", "#fee08b", "#fdae61", "#f46d43", "#d53e4f", "#9e0142"];
        const buckets = colors.length;
        const months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];

        const  minTime = d3.min(tempData, (d) => new Date(d.year,1,1,0,0));
        const  maxTime = d3.max(tempData, (d) => new Date(d.year,1,1,0,0));

        const xScale = d3.scaleTime()
            .domain([minTime, maxTime]) 
            .range([margin.left, w]);   

        const xAxis = d3.axisBottom(xScale).ticks(20);

        const svg = d3.select("#results")
            .append("svg")
            .attr("width",  w + margin.left + margin.right)
            .attr("height", h + margin.top + margin.bottom);

        const div = d3.select("body")
            .append("div")  
            .attr("class", "tooltip")               
            .style("opacity", 0);

        svg.append("g")
            .attr("transform", "translate(0," + (h+margin.top) + ")")
            .call(xAxis);

        const monthsLabels = svg.selectAll("monthLabel")
            .data(months)
            .enter()
            .append("text")
            .text((d) => d)
            .attr("x", 100)
            .attr("y", (d,i) => i * h/12 + 21)
            .style("text-anchor", "end")
            .attr("transform", "translate(-40," +0+ ")")
            .style("font-size", 10);

        const colorScale = d3.scaleQuantile()
          .domain([d3.min(tempData, (d) => d.variance + baseTemperature ), d3.max(tempData, (d) => d.variance + baseTemperature )])
          .range(colors);

        const heatMap = svg.selectAll("month")
          .data(tempData, (d) => d);

        const rects = heatMap.enter()
          .append("rect")
          .attr("x", (d) => xScale(new Date(d.year,1,1,0,0)))
          .attr("y", (d) => d.month * h/12 - margin.bottom + margin.top -1)
          .attr("width", barWidth + 3)
          .attr("height", h/12 )
          .style("fill", colors[0])
          .on("mouseover", function(d) {        
            div.transition()        
                .duration(200)      
                .style("opacity", .9);      
            div .html( d.year +" "+ months[d.month-1]+"<br>"+(d.variance + baseTemperature).toFixed(3)+"    &deg;C  <br>"+d.variance+" Variance")   
                .style("left", (d3.event.pageX) + "px")     
                .style("top", (d3.event.pageY - 50) + "px");    
            })                  
            .on("mouseout", function(d) {       
            div.transition()        
                .duration(500)      
                .style("opacity", 0);   
            });

      rects.transition().duration(1000)
          .style("fill", (d) => colorScale(d.variance + baseTemperature));

          svg.append("text")             
              .attr("transform",
                    "translate(" + (w/2) + " ," + 
                    (h+ margin.top + 45) + ")")
              .style("text-anchor", "middle")
              .text("Years");

          svg.append("text")
              .attr("transform", "rotate(-90)")
              .attr("y", -5)
              .attr("x",0 - (h / 2))
              .attr("dy", "1em")
              .style("text-anchor", "middle")
              .text("Months");   

       const legend = svg.selectAll("legend")
          .data([0].concat(colorScale.quantiles()), (d) => d);

       const legendEntries = legend.enter().append("g")
              .attr("class", "legend");

          legendEntries.append("rect")
            .attr("x", (d, i)  => (w*0.7)+ legendElementWidth/4 * i )
            .attr("y", h + 40)
            .attr("width", legendElementWidth)
            .attr("height", 20)
            .style("fill", (d, i) => colors[i]);

          legendEntries.append("text")
            .data(tempData)
            .text((d) => "≥ " + Math.round(d.variance+baseTemperature))
            .attr("x", (d, i) =>(w*0.7)+ legendElementWidth/4 * i)
            .attr("y", h + 75);
    }

</script>

Answer 1

此代码导致您出现问题：

   const legend = svg.selectAll("legend")
      .data(tempData.concat(colorScale.quantiles()), (d) => d["month"] );

      legend.enter().append("g")
          .attr("class", "legend");

      legend.append("rect")
        .attr("x", (d,i)  => legendElementWidth * i)
        .attr("y", h)
        .attr("width", legendElementWidth)
        .attr("height", 5)
        .style("fill", (d, i) => colors[i]);

      legend.append("text")
        .attr("class", "mono")
        .text((d) => "≥ " + Math.round(d.variance+baseTemperature))
        .attr("x", (d, i) =>legendElementWidth * i)
        .attr("y", h + 4);

请注意，您的输入选择仅用于附加＆＃39; g＆＃39;元素。您还需要使用输入选择附加矩形和文本。将您的代码与：

对比

   const legend = svg.selectAll("legend")
      .data(tempData.concat(colorScale.quantiles()), (d) => d["month"] );

   const legendEntries = legend.enter().append("g")
          .attr("class", "legend");

      legendEntries.append("rect")
        .attr("x", (d,i)  => legendElementWidth * i)
        .attr("y", h)
        .attr("width", legendElementWidth)
        .attr("height", 5)
        .style("fill", (d, i) => colors[i]);

      legendEntries.append("text")
        .attr("class", "mono")
        .text((d) => "≥ " + Math.round(d.variance+baseTemperature))
        .attr("x", (d, i) =>legendElementWidth * i)
        .attr("y", h + 4);

输入选择返回需要添加到DOM的元素。在这里，我们为每个需要添加的元素附加一个＆＃39;及其数据。然后我们将项目附加到我们刚刚输入的内容中。

这不是您问题的一部分，但您可能想要检查传递给图例的数据。

D3：为什么没有出现热图颜色图例？

1 个答案: