Question

试图了解mbostock的例子（here），我遇到了一个奇怪的问题：

使用CSV数据（加载d3.csv()），一切都很完美。使用d3.json()时，我得到＆＃34;无法读取属性＆＃39;长度＆＃39;未定义的使用JSON数据＆＃34; 我们正在使用相同的数据格式说出相同的数据，只是使用在线convertcsv进行转换，数据也通过了JSONLint验证。

（我在json中使用csv和对象读过类似帖子及其相关答案，但是使用原生的d3.csv()和d3.json()函数，不应该得到结果数据对象是一样的吗？）

CSV数据：

date,price
Jan 2000,1394.46
Feb 2000,1366.42
Mar 2000,1498.58
Apr 2000,1452.43
May 2000,1420.6
Jun 2000,1454.6
Jul 2000,1430.83
Aug 2000,1517.68
Sep 2000,1436.51
Oct 2000,1429.4
Nov 2000,1314.95
Dec 2000,1320.28

转换后的JSON：

[
  {
    "date":"Jan 2000",
    "price":1394.46
  },
  {
    "date":"Feb 2000",
    "price":1366.42
  },
  {
    "date":"Mar 2000",
    "price":1498.58
  },
  {
    "date":"Apr 2000",
    "price":1452.43
  },
  {
    "date":"May 2000",
    "price":1420.6
  },
  {
    "date":"Jun 2000",
    "price":1454.6
  },
  {
    "date":"Jul 2000",
    "price":1430.83
  },
  {
    "date":"Aug 2000",
    "price":1517.68
  },
  {
    "date":"Sep 2000",
    "price":1436.51
  },
  {
    "date":"Oct 2000",
    "price":1429.4
  },
  {
    "date":"Nov 2000",
    "price":1314.95
  },
  {
    "date":"Dec 2000",
    "price":1320.28
  }
]

最后，代码是：

<!DOCTYPE html>
<meta charset="utf-8">
<style>

svg {
  font: 10px sans-serif;
}

.area {
  fill: steelblue;
  clip-path: url(#clip);
}

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

.brush .extent {
  stroke: #fff;
  fill-opacity: .125;
  shape-rendering: crispEdges;
}

</style>
<body>
<script src="..\d3.v3.min.js"></script>
<script>

var margin = {top: 10, right: 10, bottom: 100, left: 40},
    margin2 = {top: 430, right: 10, bottom: 20, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom,
    height2 = 500 - margin2.top - margin2.bottom;

var parseDate = d3.time.format("%b %Y").parse;

var x = d3.time.scale().range([0, width]),
    x2 = d3.time.scale().range([0, width]),
    y = d3.scale.linear().range([height, 0]),
    y2 = d3.scale.linear().range([height2, 0]);

var xAxis = d3.svg.axis().scale(x).orient("bottom"),
    xAxis2 = d3.svg.axis().scale(x2).orient("bottom"),
    yAxis = d3.svg.axis().scale(y).orient("left");

var brush = d3.svg.brush()
    .x(x2)
    .on("brush", brushed);

var area = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x(d.date); })
    .y0(height)
    .y1(function(d) { return y(d.price); });

var area2 = d3.svg.area()
    .interpolate("monotone")
    .x(function(d) { return x2(d.date); })
    .y0(height2)
    .y1(function(d) { return y2(d.price); });

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom);

svg.append("defs").append("clipPath")
    .attr("id", "clip")
  .append("rect")
    .attr("width", width)
    .attr("height", height);

var focus = svg.append("g")
    .attr("class", "focus")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var context = svg.append("g")
    .attr("class", "context")
    .attr("transform", "translate(" + margin2.left + "," + margin2.top + ")");

d3.json("singlestock.json", type, function(error, data) {
//d3.csv("singlestock.csv", type, function(error, data) {
  x.domain(d3.extent(data.map(function(d) { return d.date; })));
  y.domain([price, d3.max(data.map(function(d) { return d.price; }))]);
  x2.domain(x.domain());
  y2.domain(y.domain());

  focus.append("path")
      .datum(data)
      .attr("class", "area")
      .attr("d", area);

  focus.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

  focus.append("g")
      .attr("class", "y axis")
      .call(yAxis);

  context.append("path")
      .datum(data)
      .attr("class", "area")
      .attr("d", area2);

  context.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height2 + ")")
      .call(xAxis2);

  context.append("g")
      .attr("class", "x brush")
      .call(brush)
    .selectAll("rect")
      .attr("y", -6)
      .attr("height", height2 + 7);
});

function brushed() {
  x.domain(brush.empty() ? x2.domain() : brush.extent());
  focus.select(".area").attr("d", area);
  focus.select(".x.axis").call(xAxis);
}

function type(d) {
  d.date = parseDate(d.date);
  d.price = +d.price;
  return d;
}

</script>

（几乎100％来自mbostock＆＃39;示例here）在代码中，只需取消注释要从CSV切换到JSON的唯一注释行。

- - - - --- EDIT 根据尼古什的回答：问题以这种方式解决了：

d3.json("singlestock.json",  function(error, data) {
        data.forEach(function(d) {
        d.date = parseDate(d.date);
        d.price = +d.price;
        d.NAgg = +d.NAgg;
    });

Answer 1

比较d3.json

的签名

d3.json(url[, callback])

和你的实际通话

d3.json("singlestock.json", type, function(error, data) {... });

您忘记从参数中删除type，请使用

d3.json("singlestock.json", function(error, data) {... })

d3.csv vs d3.json：无法读取属性＆＃39;长度＆＃39;未定义的使用JSON数据

1 个答案: