---
id: 587d7fac367417b2b2512bde
title: Use a Pre-Defined Scale to Place Elements
required:
  - src: 'https://cdnjs.cloudflare.com/ajax/libs/d3/4.3.0/d3.min.js'
challengeType: 6
videoUrl: ''
localeTitle: 使用预定义比例放置元素
---

## Description
<section id="description">设置了比例后，就可以再次绘制散点图。比例就像处理函数一样，可以将x和y原始数据转换为适合SVG画布上正确渲染的值。他们将数据保存在屏幕的绘图区域内。使用缩放功能设置SVG形状的坐标属性值。这包括<code>rect</code>或<code>text</code>元素的<code>x</code>和<code>y</code>属性，或者<code>circles</code> <code>cx</code>和<code>cy</code> 。这是一个例子： <blockquote>形状<br> .attr（“x”，（d）=&gt; xScale（d [0]）） </blockquote> Scales设置形状坐标属性以将数据点放置到SVG画布上。显示实际数据值时不需要应用比例，例如，在工具提示或标签的<code>text()</code>方法中。 </section>

## Instructions
<section id="instructions">使用<code>xScale</code>和<code>yScale</code>将<code>circle</code>和<code>text</code>形状定位到SVG画布上。对于<code>circles</code> ，应用比例来设置<code>cx</code>和<code>cy</code>属性。给它们半径5个单位。对于<code>text</code>元素，应用比例来设置<code>x</code>和<code>y</code>属性。标签应偏移到点的右侧。要执行此操作，请在将x数据传递给<code>xScale</code>之前将其添加10个单位。 </section>

## Tests
<section id='tests'>

```yml
tests:
  - text: 您的代码应该有10个<code>circle</code>元素。
    testString: 'assert($("circle").length == 10, "Your code should have 10 <code>circle</code> elements.");'
  - text: 应用刻度后，第一个<code>circle</code>元素应具有大约91的<code>cx</code>值和大约368的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(0).attr("cx")) == "91" && Math.round($("circle").eq(0).attr("cy")) == "368" && $("circle").eq(0).attr("r") == "5", "The first <code>circle</code> element should have a <code>cx</code> value of approximately 91 and a <code>cy</code> value of approximately 368 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第二个<code>circle</code>元素的<code>cx</code>值应约为159， <code>cy</code>值应约为181。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(1).attr("cx")) == "159" && Math.round($("circle").eq(1).attr("cy")) == "181" && $("circle").eq(1).attr("r") == "5", "The second <code>circle</code> element should have a <code>cx</code> value of approximately 159 and a <code>cy</code> value of approximately 181 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第三个<code>circle</code>元素应具有约340的<code>cx</code>值和约329的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(2).attr("cx")) == "340" && Math.round($("circle").eq(2).attr("cy")) == "329" && $("circle").eq(2).attr("r") == "5", "The third <code>circle</code> element should have a <code>cx</code> value of approximately 340 and a <code>cy</code> value of approximately 329 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第四个<code>circle</code>元素应具有大约131的<code>cx</code>值和大约60的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(3).attr("cx")) == "131" && Math.round($("circle").eq(3).attr("cy")) == "60" && $("circle").eq(3).attr("r") == "5", "The fourth <code>circle</code> element should have a <code>cx</code> value of approximately 131 and a <code>cy</code> value of approximately 60 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第五个<code>circle</code>元素应具有大约440的<code>cx</code>值和大约237的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(4).attr("cx")) == "440" && Math.round($("circle").eq(4).attr("cy")) == "237" && $("circle").eq(4).attr("r") == "5", "The fifth <code>circle</code> element should have a <code>cx</code> value of approximately 440 and a <code>cy</code> value of approximately 237 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第六个<code>circle</code>元素应具有约271的<code>cx</code>值和约306的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(5).attr("cx")) == "271" && Math.round($("circle").eq(5).attr("cy")) == "306" && $("circle").eq(5).attr("r") == "5", "The sixth <code>circle</code> element should have a <code>cx</code> value of approximately 271 and a <code>cy</code> value of approximately 306 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第七个<code>circle</code>元素的<code>cx</code>值约为361， <code>cy</code>值约为351。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(6).attr("cx")) == "361" && Math.round($("circle").eq(6).attr("cy")) == "351" && $("circle").eq(6).attr("r") == "5", "The seventh <code>circle</code> element should have a <code>cx</code> value of approximately 361 and a <code>cy</code> value of approximately 351 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第八个<code>circle</code>元素应具有约261的<code>cx</code>值和约132的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(7).attr("cx")) == "261" && Math.round($("circle").eq(7).attr("cy")) == "132" && $("circle").eq(7).attr("r") == "5", "The eighth <code>circle</code> element should have a <code>cx</code> value of approximately 261 and a <code>cy</code> value of approximately 132 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第九个<code>circle</code>元素应具有大约131的<code>cx</code>值和大约144的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(8).attr("cx")) == "131" && Math.round($("circle").eq(8).attr("cy")) == "144" && $("circle").eq(8).attr("r") == "5", "The ninth <code>circle</code> element should have a <code>cx</code> value of approximately 131 and a <code>cy</code> value of approximately 144 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 应用刻度后，第十个<code>circle</code>元素应具有大约79的<code>cx</code>值和大约326的<code>cy</code>值。它的<code>r</code>值也应为5。
    testString: 'assert(Math.round($("circle").eq(9).attr("cx")) == "79" && Math.round($("circle").eq(9).attr("cy")) == "326" && $("circle").eq(9).attr("r") == "5", "The tenth <code>circle</code> element should have a <code>cx</code> value of approximately 79 and a <code>cy</code> value of approximately 326 after applying the scales. It should also have an <code>r</code> value of 5.");'
  - text: 您的代码应该有10个<code>text</code>元素。
    testString: 'assert($("text").length == 10, "Your code should have 10 <code>text</code> elements.");'
  - text: 应用刻度后，第一个标签的<code>x</code>值约为100， <code>y</code>值约为368。
    testString: 'assert(Math.round($("text").eq(0).attr("x")) == "100" && Math.round($("text").eq(0).attr("y")) == "368", "The first label should have an <code>x</code> value of approximately 100 and a <code>y</code> value of approximately 368 after applying the scales.");'
  - text: 第二标签应该有一个<code>x</code>的大约168值和<code>y</code>施加鳞后的约181的值。
    testString: 'assert(Math.round($("text").eq(1).attr("x")) == "168" && Math.round($("text").eq(1).attr("y")) == "181", "The second label should have an <code>x</code> value of approximately 168 and a <code>y</code> value of approximately 181 after applying the scales.");'
  - text: 应用刻度后，第三个标签的<code>x</code>值约为350， <code>y</code>值约为329。
    testString: 'assert(Math.round($("text").eq(2).attr("x")) == "350" && Math.round($("text").eq(2).attr("y")) == "329", "The third label should have an <code>x</code> value of approximately 350 and a <code>y</code> value of approximately 329 after applying the scales.");'
  - text: 第四标签应该有一个<code>x</code>的大约141值和<code>y</code>施加鳞后的约60的值。
    testString: 'assert(Math.round($("text").eq(3).attr("x")) == "141" && Math.round($("text").eq(3).attr("y")) == "60", "The fourth label should have an <code>x</code> value of approximately 141 and a <code>y</code> value of approximately 60 after applying the scales.");'
  - text: 应用刻度后，第五个标签的<code>x</code>值约为449， <code>y</code>值约为237。
    testString: 'assert(Math.round($("text").eq(4).attr("x")) == "449" && Math.round($("text").eq(4).attr("y")) == "237", "The fifth label should have an <code>x</code> value of approximately 449 and a <code>y</code> value of approximately 237 after applying the scales.");'
  - text: 应用刻度后，第六个标签的<code>x</code>值约为280， <code>y</code>值约为306。
    testString: 'assert(Math.round($("text").eq(5).attr("x")) == "280" && Math.round($("text").eq(5).attr("y")) == "306", "The sixth label should have an <code>x</code> value of approximately 280 and a <code>y</code> value of approximately 306 after applying the scales.");'
  - text: 应用刻度后，第七个标签的<code>x</code>值约为370， <code>y</code>值约为351。
    testString: 'assert(Math.round($("text").eq(6).attr("x")) == "370" && Math.round($("text").eq(6).attr("y")) == "351", "The seventh label should have an <code>x</code> value of approximately 370 and a <code>y</code> value of approximately 351 after applying the scales.");'
  - text: 应用刻度后，第八个标签的<code>x</code>值约为270， <code>y</code>值约为132。
    testString: 'assert(Math.round($("text").eq(7).attr("x")) == "270" && Math.round($("text").eq(7).attr("y")) == "132", "The eighth label should have an <code>x</code> value of approximately 270 and a <code>y</code> value of approximately 132 after applying the scales.");'
  - text: 应用刻度后，第九个标签的<code>x</code>值约为140， <code>y</code>值约为144。
    testString: 'assert(Math.round($("text").eq(8).attr("x")) == "140" && Math.round($("text").eq(8).attr("y")) == "144", "The ninth label should have an <code>x</code> value of approximately 140 and a <code>y</code> value of approximately 144 after applying the scales.");'
  - text: 应用刻度后，第十个标签的<code>x</code>值约为88， <code>y</code>值约为326。
    testString: 'assert(Math.round($("text").eq(9).attr("x")) == "88" && Math.round($("text").eq(9).attr("y")) == "326", "The tenth label should have an <code>x</code> value of approximately 88 and a <code>y</code> value of approximately 326 after applying the scales.");'

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='html-seed'>

```html
<body>
  <script>
    const dataset = [
                  [ 34,     78 ],
                  [ 109,   280 ],
                  [ 310,   120 ],
                  [ 79,   411 ],
                  [ 420,   220 ],
                  [ 233,   145 ],
                  [ 333,   96 ],
                  [ 222,    333 ],
                  [ 78,    320 ],
                  [ 21,   123 ]
                ];

    const w = 500;
    const h = 500;
    const padding = 60;

    const xScale = d3.scaleLinear()
                     .domain([0, d3.max(dataset, (d) => d[0])])
                     .range([padding, w - padding]);

    const yScale = d3.scaleLinear()
                     .domain([0, d3.max(dataset, (d) => d[1])])
                     .range([h - padding, padding]);

    const svg = d3.select("body")
                  .append("svg")
                  .attr("width", w)
                  .attr("height", h);

    svg.selectAll("circle")
       .data(dataset)
       .enter()
       .append("circle")
       // Add your code below this line



       // Add your code above this line

    svg.selectAll("text")
       .data(dataset)
       .enter()
       .append("text")
       .text((d) =>  (d[0] + ", "
 + d[1]))
       // Add your code below this line



       // Add your code above this line
  </script>
</body>

```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>