如何在D3 JS中使用填充属性中的色标？

Question

我在D3 JS中制作热图，其中沿X轴为Year，沿Y轴为Month。 每个单元格都是温度，并基于此获得不同的“填充”颜色。 我的问题是如何制作一个使用一系列颜色代码映射minTemp / maxTemp域的色标。 到目前为止我有下面的代码，但这不起作用：

var url = "https://raw.githubusercontent.com/FreeCodeCamp/ProjectReferenceData/master/global-temperature.json"

d3.json(url, function(json){

  //load data from API and save in variable data
  var data = json.monthlyVariance;
  var baseTemp = json.baseTemperature;

  //Add temperature to each object in data set
  for(var i = 0; i < data.length; i++){

    var temperature = baseTemp + data[i].variance  
    data[i].temperature = temperature;

    var monthString = "";
    switch(data[i].month){

      case 1:
        data[i].monthString = "January";
        break;
      case 2:
        data[i].monthString = "February";
        break;
      case 3:
        data[i].monthString = "March";
        break;
      case 4:
        data[i].monthString = "April";
        break;
      case 5:
        data[i].monthString = "May";
        break;
      case 6:
        data[i].monthString = "June";
        break;
      case 7:
        data[i].monthString = "July";
        break;
      case 8:
        data[i].monthString = "August";
        break;
      case 9:
        data[i].monthString = "September";
        break;
      case 10:
        data[i].monthString = "October";
        break;  
      case 11:
        data[i].monthString = "November";
        break;
      case 12:
        data[i].monthString = "December";
        break;
    }


  }

  //Set dimensions of div container, svg, and chart area(g element)
  var margin = {top: 20, right: 40, bottom: 40, left: 80};

  //Width of the chart, within SVG element
  var w = 1000 - margin.left - margin.right;
  //Height of the chart, within SVG element
  var h = 500 - margin.top - margin.bottom;

  //Create SVG element and append to #chart div container
  var svg = d3.select("#chart")
              .append("svg")
                .attr("width", w + margin.left + margin.right)
                .attr("height", h + margin.top + margin.bottom)
              .append("g")
                .attr("transform", "translate(" + margin.left + "," + margin.top + ")");


  //Get Min Max values
  var maxYear = d3.max(data, function(d){

      return d.year;

  });

  var minYear = d3.min(data, function(d){

      return d.year;

  });

  var maxTemp = d3.max(data, function(d){

    return d.temperature;

  });     

  var minTemp = d3.min(data, function(d){

    return d.temperature;

  })

  //Create X scale, axis and label
  var xScale = d3.scaleLinear()
                 .domain([minYear, maxYear])
                 .range([0,w]);

  var xAxis = d3.axisBottom()
                .scale(xScale)
                .ticks(20)
                .tickFormat(d3.format("d"));

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

  //Create Y scale, axis and label

  var cellHeight = (h / 12);

  var yRange = [];

  for(var i = 0; i < 12 ; i++){

      yRange.push(i * cellHeight);

  }

  var yScale = d3.scaleOrdinal()
                 .domain(["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"])
                 .range(yRange);

  var yAxis = d3.axisLeft()
                .scale(yScale)
                .ticks(12);

  svg.append("g")
  //append a g element
     .attr("class", "axis")
     .call(yAxis)
      //call yAxis function on this g element
     .selectAll(".tick text")
     //select all elements with class tick and nested text element
     .attr("transform", "translate(0," + (cellHeight/2) + ")");
     //move all text elements half a cell height down

  //Create color scale
  var colors = d3.scaleOrdinal()
                 .domain([minTemp,maxTemp])
                 .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]);

  //Select all rect elements in G container element, bind data and append
  var cells = svg.selectAll("cells")
                 .data(data)
                 .enter()
                 .append("rect");


  var cellAttributes = cells
                        .attr("x", function(d){

                          return xScale(d.year);

                        })
                        .attr("y", function(d){

                          return yScale(d.monthString);

                        })
                        .attr("width", w/(maxYear-minYear))
                        .attr("height", h/12)
                        .attr("fill", function(d){

                          return colors(d);

                        })
                        .attr("class", "cell");


});

我可以在fill属性函数中编写一个long if / else语句，将温度映射到颜色代码，但这不是我认为的“D3方式”。 我怎么能用比例做？：

  var colors = d3.scaleOrdinal()
                 .domain([minTemp,maxTemp])
                 .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]);

Answer 1

你不需要这里的顺序尺度。 您需要量化比例：

量化标度类似于线性标度，除了它们使用离散而非连续范围。 基于输出范围中的值的数量（即，基数），将连续输入域划分为均匀段。

因此，这应该是你的规模：

var colors = d3.scaleQuantize()
    .domain([minTemp,maxTemp])
    .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", 
    "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]);

这是一个演示：

 var data = d3.range(50); var colors = d3.scaleQuantize() .domain([0,50]) .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]); var svg = d3.select("svg"); var rects = svg.selectAll(".rects") .data(data) .enter() .append("rect") .attr("y", 10) .attr("height", 100) .attr("x", (d,i)=>10 + i*9) .attr("width", 6) .attr("fill", d=>colors(d)) .attr("stroke", "gray"); 

 <script src="https://d3js.org/d3.v4.min.js"></script> <svg width="500"></svg> 

您还可以使用scaleLinear ，它具有在颜色之间进行插值的优点（因此，您的颜色数组中将包含多于11种颜色）。 但是，请注意使用d3.ticks在域中设置相同数量的元素：

d3.ticks(minTemp, maxTemp, 11);

这是一个scaleLinear的演示：

 var data = d3.range(50); var colors = d3.scaleLinear() .domain(d3.ticks(0, 50, 11)) .range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]); var svg = d3.select("svg"); var rects = svg.selectAll(".rects") .data(data) .enter() .append("rect") .attr("y", 10) .attr("height", 100) .attr("x", (d,i)=>10 + i*9) .attr("width", 6) .attr("fill", d=>colors(d)) .attr("stroke", "gray"); 

 <script src="https://d3js.org/d3.v4.min.js"></script> <svg width="500"></svg> 

Answer 2

非常感谢你的帮助，以下是我最终的表现：

演示： http ： //codepen.io/chemok78/full/qRXmWX/

var url = "https://raw.githubusercontent.com/FreeCodeCamp/ProjectReferenceData/master/global-temperature.json"

d3.json(url, function(json) {

  //load data from API and save in variable data
  var data = json.monthlyVariance;
  var baseTemp = json.baseTemperature;

  var months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];

  //Add temperature to each object in data set
  for (var i = 0; i < data.length; i++) {

    var temperature = baseTemp + data[i].variance
    data[i].temperature = temperature;

    var monthString = "";
    switch (data[i].month) {

      case 1:
        data[i].monthString = "January";
        break;
      case 2:
        data[i].monthString = "February";
        break;
      case 3:
        data[i].monthString = "March";
        break;
      case 4:
        data[i].monthString = "April";
        break;
      case 5:
        data[i].monthString = "May";
        break;
      case 6:
        data[i].monthString = "June";
        break;
      case 7:
        data[i].monthString = "July";
        break;
      case 8:
        data[i].monthString = "August";
        break;
      case 9:
        data[i].monthString = "September";
        break;
      case 10:
        data[i].monthString = "October";
        break;
      case 11:
        data[i].monthString = "November";
        break;
      case 12:
        data[i].monthString = "December";
        break;
    }


  }

  //Set dimensions of div container, svg, and chart area(g element)
  var margin = {
    top: 40,
    right: 60,
    bottom: 100,
    left: 100
  };

  //Width of the chart, within SVG element
  var w = 1000 - margin.left - margin.right;
  //Height of the chart, within SVG element
  var h = 600 - margin.top - margin.bottom;

  //Create SVG element and append to #chart div container
  //SVG is nested G element
  var svg = d3.select("#chart")
    .append("svg")
    .attr("width", w + margin.left + margin.right)
    .attr("height", h + margin.top + margin.bottom)
    .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");


  //Get Min Max values
  var maxYear = d3.max(data, function(d) {

    return d.year;

  });

  var minYear = d3.min(data, function(d) {

    return d.year;

  });


  var maxTemp = d3.max(data, function(d) {

    return d.temperature;

  });

  var minTemp = d3.min(data, function(d) {

    return d.temperature;

  })


  //Create X scale, axis and label
  var xScale = d3.scaleLinear()
    .domain([minYear, maxYear])
    .range([0, w]);

  var xAxis = d3.axisBottom()
    .scale(xScale)
    .ticks(20)
    .tickFormat(d3.format("d"));

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

  var xLabel = svg.append("text")
    .text("Year")
    .attr("x", w / 2)
    .attr("y", h + (margin.bottom / 2.5))
    .attr("font-size", "14px");

  //Create Y scale, axis and label

  var cellHeight = (h / 12);

  var yRange = [];

  for (var i = 0; i < 12; i++) {

    yRange.push(i * cellHeight);

  }


  var yScale = d3.scaleOrdinal()
    .domain(months)
    .range(yRange);

  var yAxis = d3.axisLeft()
    .scale(yScale)
    .ticks(12);

  svg.append("g")
    //append a g element
    .attr("class", "axis")
    .call(yAxis)
    //call yAxis function on this g element
    .selectAll(".tick text")
    //select all elements with class tick and nested text element
    .attr("transform", "translate(0," + (cellHeight / 2) + ")");
  //move all text elements half a cell height down

  var yLabel = svg.append("text")
    .attr("transform", "rotate(-90)")
    .attr("x", 0 - (h / 2))
    .attr("y", 0 - (margin.left / 1.8))
    .style("font-size", "14px")
    .style("text-anchor", "middle")
    .text("Month");


  //Create color scale

  var colorCodes = ["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"];

  var colors = d3.scaleQuantile()
    //quantize scale divides domain in bands according to ordinal scale range
    .domain([minTemp, maxTemp])
    //.domain(d3.ticks(minTemp,maxTemp,11))
    .range(colorCodes);

  var colorQuantiles = colors.quantiles();
  colorQuantiles.unshift(0);
  //save the upper ranges of each temperature quantile + 0 at the beginning (quantile function does not count 0 as start)


  //Append tooltip to chart area. Fully transparant at first
  var tip = d3.select("#chart").append("div")
    .attr("class", "tooltip")
    .style("opacity", 0);

  //Select all rect elements in G container element, bind data and append
  var cells = svg.selectAll("cells")
    .data(data)
    .enter()
    .append("rect");

  var cellAttributes = cells
    .attr("x", function(d) {

      return xScale(d.year);

    })
    .attr("y", function(d) {

      return yScale(d.monthString);

    })
    .attr("width", w / (maxYear - minYear))
    .attr("height", cellHeight)
    .attr("fill", function(d) {

      return colors(d.temperature);

    })
    .attr("class", "cell")
    .on("mouseover", function(d) {

      tip.transition()
        .style("opacity", 0.7);
      tip.html("<strong>" + months[d.month - 1] + " - " + d.year + "</strong><br>" + d.temperature.toFixed(2) + " °C<br>" + d.variance.toFixed(2) + " °C")
        .style("left", d3.event.pageX + "px")
        .style("top", d3.event.pageY - 70 + "px");

    })
    .on("mouseout", function(d) {

      tip.transition()
        .style("opacity", 0);

    })

  //Create a legend

  var blockWidth = 35;
  var blockHeight = 20;

  var legend = svg.selectAll(".legend")
    .data(colorQuantiles)
    .enter()
    .append("g")
    .attr("class", "legend")
    .attr("font-size", "14px")
    .attr("font-style", "PT Sans")
    .attr("transform", function(d, i) {

      return ("translate(" + i * blockWidth + ",0)")

    });

  legend.append("rect")
    .attr("x", (w / 5) * 3)
    .attr("y", h + (margin.bottom / 3))
    .attr("width", blockWidth)
    .attr("height", blockHeight)
    .style("fill", function(d, i) {

      return (colorCodes[i]);

    });

  legend.append("text")
    .attr("x", ((w / 5) * 3) + (blockWidth / 2))
    .attr("y", (h + (margin.bottom / 3)) + blockHeight + 15)
    .text(function(d, i) {

      return colorQuantiles[i].toFixed(1);

    })
    .style("text-anchor", "middle");

})