2018-10-10 22:03:03 +00:00
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---
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id: 587d7fa9367417b2b2512bcf
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2021-03-09 15:51:59 +00:00
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title: 动态更改每个条形的高度
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2018-10-10 22:03:03 +00:00
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challengeType: 6
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2020-09-17 16:13:05 +00:00
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forumTopicId: 301486
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2021-01-13 02:31:00 +00:00
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dashedName: dynamically-change-the-height-of-each-bar
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2021-03-09 15:51:59 +00:00
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和动态设置 `x` 值一样，也可以把每个条形的高度设置成数组中数据点的值。
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2020-09-17 16:13:05 +00:00
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```js
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selection.attr("property", (d, i) => {
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2021-03-09 15:51:59 +00:00
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2020-09-17 16:13:05 +00:00
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})
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```
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2021-03-09 15:51:59 +00:00
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`d` 是数据点值，`i` 是数组中数据点的索引。
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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改变 `height` 属性的回调函数，让它返回数据值乘以 3 的值。
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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**注意：** 记住，把所有数据点乘以相同的常数来对数据进行缩放（就像放大）， 这有利于看清例子中条形数值之间的差异。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第一个 `rect` 的 `height` 应为 `36`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(0).attr('height') == '36');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第二个 `rect` 的 `height` 应为 `93`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(1).attr('height') == '93');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第三个 `rect` 的 `height` 应为 `66`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(2).attr('height') == '66');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第四个 `rect` 的 `height` 应为 `51`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(3).attr('height') == '51');
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2018-10-10 22:03:03 +00:00
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```
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2021-03-09 15:51:59 +00:00
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第五个 `rect` 的 `height` 应为 `75`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(4).attr('height') == '75');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第六个 `rect` 的 `height` 应为 `54`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(5).attr('height') == '54');
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```
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2018-10-10 22:03:03 +00:00
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2021-03-09 15:51:59 +00:00
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第七个 `rect` 的 `height` 应为 `87`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(6).attr('height') == '87');
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```
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2020-09-17 16:13:05 +00:00
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2021-03-09 15:51:59 +00:00
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第八个 `rect` 的 `height` 应为 `42`。
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2020-09-17 16:13:05 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(7).attr('height') == '42');
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```
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2020-09-17 16:13:05 +00:00
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2021-03-09 15:51:59 +00:00
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第九个 `rect` 的 `height` 应为 `27`。
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2020-09-17 16:13:05 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('rect').eq(8).attr('height') == '27');
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2018-10-10 22:03:03 +00:00
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```
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2020-08-13 15:24:35 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --seed-contents--
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```html
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<body>
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<script>
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const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
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const w = 500;
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const h = 100;
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const svg = d3.select("body")
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.append("svg")
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.attr("width", w)
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.attr("height", h);
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svg.selectAll("rect")
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.data(dataset)
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.enter()
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.append("rect")
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.attr("x", (d, i) => i * 30)
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.attr("y", 0)
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.attr("width", 25)
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.attr("height", (d, i) => {
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// Add your code below this line
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// Add your code above this line
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});
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</script>
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</body>
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```html
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<body>
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<script>
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const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
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const w = 500;
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const h = 100;
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const svg = d3.select("body")
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.append("svg")
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.attr("width", w)
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.attr("height", h);
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svg.selectAll("rect")
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.data(dataset)
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.enter()
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.append("rect")
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.attr("x", (d, i) => i * 30)
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.attr("y", 0)
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.attr("width", 25)
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.attr("height", (d, i) => {
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return d * 3
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});
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</script>
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</body>
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```
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