如何在D3 JS中使用填充属性中的色标？

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"]);

Gerardo Furt.. 14

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");

d3.ticks(minTemp, maxTemp, 11);

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");

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

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");