我正在用 D3 JS 制作热图，X 轴为年，Y 轴为月。每个单元格都是一个温度，并基于此获得不同的“填充”颜色。我的问题是如何制作一个色标来映射具有一系列颜色代码的 minTemp/maxTemp 域。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");
});
我可以在填充属性函数中写一个很长的 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”。我怎样才能用秤做到这一点？:
var colors = d3.scaleOrdinal()
.domain([minTemp,maxTemp])
.range(["#5E4FA2", "#3288BD", "#66C2A5", "#ABDDA4", "#E6F598", "#FFFFBF", "#FEE08B", "#FDAE61", "#F46D43", "#D53E4F", "#9E0142"]);
最佳答案
这里不需要序数尺度。你需要一个 quantize改为缩放:
Quantize scales are similar to linear scales, except they use a discrete rather than continuous range. The continuous input domain is divided into uniform segments based on the number of values in (i.e., the cardinality of) the output range.
因此，这应该是您的体重秤:
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，颜色数组中的颜色将超过 11 种)。但是要注意在域中设置相同数量的元素，使用d3.ticks:
d3.ticks(minTemp, maxTemp, 11);
这是一个使用 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>关于javascript - 如何在 D3 JS 中制作色标以用于填充属性？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41848677/