javascript - 如何从基线得出百分比？

Question

我想根据每个数据点与平均值的距离绘制一个简单的折线图。 (高于、低于 % 等)。我正在为它建模 this

我似乎想不通的两个问题—— 为什么我的线稿没有？我已经浏览了每一行，但似乎无法弄清楚。

其次，如何去掉y轴上的off-scaling？缩放似乎都没有异常，我无法修复它。我认为这与缩放有关。

var x = d3.time.scale()
.range([0, width]);

var y = d3.scale.log()
.range([height, 0]);

  x.domain(d3.extent(data, function(d) { return d.date; }));
  y.domain(d3.extent(data, function(d) { return d.ratio; }));

Here's my CodePen

我可能遗漏了什么？我认为这是我还没有了解 d3 的东西。非常感谢!!

Answer 1

关于路径，代码中存在三个问题:

1. 解析器命名为parseDate，而不是parseTime；

2. 您必须先解析字符串，然后才将其传递给 x 标度，而不是相反:

   line.x(function(d) { return x(parseDate(d.date)); });
   

3. 您必须解析字符串以设置域:

   x.domain(d3.extent(data, function(d) { return parseDate(d.date); }));
   

这是更新的 CodePen:https://codepen.io/anon/pen/qMbRoQ?editors=0011

这是一个正在运行的片段:

var data = [{
    "date": "2018-08-22T14:53:37.267Z",
    "value": 2200000
  },
  {
    "date": "2018-08-21T14:53:37.267Z",
    "value": 7400000
  },
  {
    "date": "2018-08-20T14:53:37.267Z",
    "value": 9500000
  },
  {
    "date": "2018-08-19T14:53:37.267Z",
    "value": 9700000
  },
  {
    "date": "2018-08-18T14:53:37.267Z",
    "value": 7100000
  },
  {
    "date": "2018-08-17T14:53:37.267Z",
    "value": 4300000
  },
  {
    "date": "2018-08-16T14:53:37.267Z",
    "value": 2500000
  },
  {
    "date": "2018-08-15T14:53:37.267Z",
    "value": 2000000
  },
  {
    "date": "2018-08-14T14:53:37.267Z",
    "value": 6400000
  },
  {
    "date": "2018-08-13T14:53:37.267Z",
    "value": 9500000
  },
  {
    "date": "2018-08-12T14:53:37.267Z",
    "value": 100000
  },
  {
    "date": "2018-08-11T14:53:37.267Z",
    "value": 4800000
  },
  {
    "date": "2018-08-10T14:53:37.267Z",
    "value": 1400000
  },
  {
    "date": "2018-08-09T14:53:37.267Z",
    "value": 6100000
  },
  {
    "date": "2018-08-08T14:53:37.267Z",
    "value": 4400000
  },
  {
    "date": "2018-08-07T14:53:37.267Z",
    "value": 7000000
  },
  {
    "date": "2018-08-06T14:53:37.267Z",
    "value": 6100000
  },
  {
    "date": "2018-08-05T14:53:37.267Z",
    "value": 300000
  },
  {
    "date": "2018-08-04T14:53:37.267Z",
    "value": 2900000
  },
  {
    "date": "2018-08-03T14:53:37.268Z",
    "value": 2000000
  },
  {
    "date": "2018-08-02T14:53:37.268Z",
    "value": 300000
  },
  {
    "date": "2018-08-01T14:53:37.268Z",
    "value": 800000
  },
  {
    "date": "2018-07-31T14:53:37.268Z",
    "value": 1200000
  },
  {
    "date": "2018-07-30T14:53:37.268Z",
    "value": 9000000
  },
  {
    "date": "2018-07-29T14:53:37.268Z",
    "value": 8600000
  },
  {
    "date": "2018-07-28T14:53:37.268Z",
    "value": 6900000
  },
  {
    "date": "2018-07-27T14:53:37.268Z",
    "value": 3400000
  },
  {
    "date": "2018-07-26T14:53:37.268Z",
    "value": 8100000
  },
  {
    "date": "2018-07-25T14:53:37.268Z",
    "value": 2900000
  },
  {
    "date": "2018-07-24T14:53:37.268Z",
    "value": 6400000
  }
]

var margin = {
    top: 30,
    right: 30,
    bottom: 40,
    left: 50
  },
  width = 960 - margin.left - margin.right,
  height = 500 - margin.top - margin.bottom;
var formatPercent = d3.format("+.0%"),
  formatChange = function(x) {
    return formatPercent(x - 1);
  },
  parseDate = d3.time.format("%Y-%m-%dT%H:%M:%S.%LZ").parse;
// var parseTime = d3.time.Parse("%Y-%m-%dT%H:%M:%S.%LZ");


var x = d3.time.scale()
  .range([0, width]);

var y = d3.scale.log()
  .range([height, 0]);

var xAxis = d3.svg.axis()
  .scale(x)
  .orient("bottom");

var yAxis = d3.svg.axis()
  .scale(y)
  .orient("left")
  .tickSize(-width, 0)
  .tickFormat(formatChange);

var line = d3.svg.line()
  .x(function(d) {
    return x(parseDate(d.date));
  })
  .y(function(d) {
    return y(d.ratio);
  });

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 + ")");

var gX = svg.append("g")
  .attr("class", "axis axis--x")
  .attr("transform", "translate(0," + height + ")");

var gY = svg.append("g")
  .attr("class", "axis axis--y");

gY.append("text")
  .attr("class", "axis-title")
  .attr("transform", "rotate(-90)")
  .attr("y", 6)
  .attr("dy", ".71em")
  .text("Change in Price");

var baseValue = +data[6].value;
console.log(baseValue)

data.forEach(function(d) {

  d.date = d.date;
  console.log(d.date)
  d.ratio = d.value / baseValue;
  console.log(d.ratio)
});


// Compute price relative to base value (hypothetical purchase price).


x.domain(d3.extent(data, function(d) {
  return parseDate(d.date);
}));
y.domain(d3.extent(data, function(d) {
  return d.ratio;
}));

// Use a second linear scale for ticks.
yAxis.tickValues(d3.scale.linear()
  .domain(y.domain())
  .ticks(9));

gX.call(xAxis);

gY.call(yAxis)
  .selectAll(".tick")
  .classed("tick--one", function(d) {
    return Math.abs(d - 1) < 1e-6;
  });

svg.append("path")
  .datum(data)
  .attr("class", "line")
  .attr("d", line);

.axis {
  font: 10px sans-serif;
}

.axis-title {
  text-anchor: end;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.axis--x path {
  display: none;
}

.axis--y .tick:not(.tick--one) line {
  stroke-opacity: .15;
}

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
  stroke-linejoin: round;
  stroke-linecap: round;
}

<body>
  <script src="//d3js.org/d3.v3.min.js"></script>
</body>

---

PS:关于基线问题，这不是很清楚，我建议你发布一个新问题，并附上相关解释:在 S.O. 上每个问题保持一个问题总是一个好习惯。