javascript - 使用 d3.entries 键值对绘制多折线图

Question

我想使用 d3.js 绘制多线图表。我在控制台中打印我的数据结构，它看起来像这样:

0:
  key: student1
  value: Array(50)
       0: {date : 2017-09-11 11:51,score:50}
       1: {date : 2017-09-11 12:53,score:90}
       ...

0:
  key: student2
  value: Array(50)
       0: {date : 2017-09-11 11:51,score:20}
       1: {date : 2017-09-11 12:53,score:30}
       ...

并将所有学生放在由不同线条表示的同一个图表中。 X 轴是日期，Y 轴是学生分数。

但似乎我在定义 X 和 Y 域时遇到问题，我无法通过 d.value.date 获取日期和得分值。

Answer 1

您无法通过使用 d.value.date 来获取 date 和 value 分数，因为这些值嵌套在另一个对象中。您可以展平这些对象以尝试获取域。离开this example ，如果您表示您的结构如下:

data = [
    {student: 'student1', date : '2017-09-11 11:51', score: 50},
    {student: 'student1', date : '2017-09-11 12:53', score: 90},
    ...
    {student: 'student2', date : '2017-09-11 11:51', score: 20},
    {student: 'student2', date : '2017-09-11 12:53', score: 30},
    ...
]

您可以尝试像这样定义轴:

var parseDate = d3.timeParse("%Y-%m-%d %H:%M");
var x = d3.scaleTime().range([0, width]);  
var y = d3.scaleLinear().range([height, 0]);

data.forEach(function(d) {
    d.date = parseDate(d.date);
    d.score = +d.score;
});
x.domain(d3.extent(data, function(d) { return d.date; }));
y.domain([0, d3.max(data, function(d) { return d.score; })]);

我对 d3noob 的示例进行了一些修改以适应此数据(添加了更多数据点):

// Set the dimensions of the canvas / graph
var margin = {
    top: 30,
    right: 20,
    bottom: 70,
    left: 50
  },
  width = 600 - margin.left - margin.right,
  height = 300 - margin.top - margin.bottom;

// Parse the date / time
var parseDate = d3.timeParse("%Y-%m-%d %H:%M");

// Set the ranges
var x = d3.scaleTime().range([0, width]);
var y = d3.scaleLinear().range([height, 0]);

// Define the line
var priceline = d3.line()
  .x(function(d) {
    return x(d.date);
  })
  .y(function(d) {
    return y(d.score);
  });

// Adds the svg canvas
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 + ")");

// Get the data
var data = [
  {
    student: 'student1',
    date: '2017-09-11 11:45',
    score: 60
  },
  {
    student: 'student1',
    date: '2017-09-11 11:51',
    score: 50
  },
  {
    student: 'student1',
    date: '2017-09-11 12:53',
    score: 90
  },
  {
    student: 'student1',
    date: '2017-09-11 12:57',
    score: 97
  },
  {
    student: 'student2',
    date: '2017-09-11 11:22',
    score: 10
  },
  {
    student: 'student2',
    date: '2017-09-11 11:31',
    score: 15
  },
  {
    student: 'student2',
    date: '2017-09-11 11:33',
    score: 20
  },
  {
    student: 'student2',
    date: '2017-09-11 11:38',
    score: 30
  },
  {
    student: 'student2',
    date: '2017-09-11 12:51',
    score: 45
  },
  {
    student: 'student2',
    date: '2017-09-11 12:59',
    score: 40
  }
]

data.forEach(function(d) {
  d.date = parseDate(d.date);
  d.price = +d.price;
});

// Scale the range of the data
x.domain(d3.extent(data, function(d) {
  return d.date;
}));
y.domain([0, d3.max(data, function(d) {
  return d.score;
})]);

// Nest the entries by symbol
var dataNest = d3.nest()
  .key(function(d) {
    return d.student;
  })
  .entries(data);

// set the colour scale
var color = d3.scaleOrdinal(d3.schemeCategory10);

legendSpace = width / dataNest.length; // spacing for the legend

// Loop through each symbol / key
dataNest.forEach(function(d, i) {

  svg.append("path")
    .attr("class", "line")
    .style("stroke", function() { // Add the colours dynamically
      return d.color = color(d.key);
    })
    .attr("id", 'tag' + d.key.replace(/\s+/g, '')) // assign an ID
    .attr("d", priceline(d.values));

  // Add the Legend
  svg.append("text")
    .attr("x", (legendSpace / 2) + i * legendSpace) // space legend
    .attr("y", height + (margin.bottom / 2) + 5)
    .attr("class", "legend") // style the legend
    .style("fill", function() { // Add the colours dynamically
      return d.color = color(d.key);
    })
    .on("click", function() {
      // Determine if current line is visible 
      var active = d.active ? false : true,
        newOpacity = active ? 0 : 1;
      // Hide or show the elements based on the ID
      d3.select("#tag" + d.key.replace(/\s+/g, ''))
        .transition().duration(100)
        .style("opacity", newOpacity);
      // Update whether or not the elements are active
      d.active = active;
    })
    .text(d.key);

});

// Add the X Axis
svg.append("g")
  .attr("class", "axis")
  .attr("transform", "translate(0," + height + ")")
  .call(d3.axisBottom(x));

// Add the Y Axis
svg.append("g")
  .attr("class", "axis")
  .call(d3.axisLeft(y));

body { font: 12px Arial;}

path { 
    stroke: steelblue;
    stroke-width: 2;
    fill: none;
}

.axis path,
.axis line {
    fill: none;
    stroke: grey;
    stroke-width: 1;
    shape-rendering: crispEdges;
}

.legend {
    font-size: 16px;
    font-weight: bold;
    text-anchor: middle;
}

<script src="https://d3js.org/d3.v5.min.js"></script>

希望这有帮助