131 lines
3.3 KiB
Markdown
131 lines
3.3 KiB
Markdown
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---
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id: 587d7fa9367417b2b2512bcf
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title: Dynamically Change the Height of Each Bar
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challengeType: 6
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forumTopicId: 301486
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---
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## Description
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<section id='description'>
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The height of each bar can be set to the value of the data point in the array, similar to how the <code>x</code> value was set dynamically.
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```js
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selection.attr("property", (d, i) => {
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/*
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* d is the data point value
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* i is the index of the data point in the array
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*/
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})
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```
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</section>
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## Instructions
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<section id='instructions'>
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Change the callback function for the <code>height</code> attribute to return the data value times 3.
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<strong>Note</strong><br>Remember that multiplying all data points by the same constant scales the data (like zooming in). It helps to see the differences between bar values in this example.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: The first <code>rect</code> should have a <code>height</code> of 36.
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testString: assert($('rect').eq(0).attr('height') == '36');
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- text: The second <code>rect</code> should have a <code>height</code> of 93.
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testString: assert($('rect').eq(1).attr('height') == '93');
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- text: The third <code>rect</code> should have a <code>height</code> of 66.
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testString: assert($('rect').eq(2).attr('height') == '66');
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- text: The fourth <code>rect</code> should have a <code>height</code> of 51.
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testString: assert($('rect').eq(3).attr('height') == '51');
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- text: The fifth <code>rect</code> should have a <code>height</code> of 75.
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testString: assert($('rect').eq(4).attr('height') == '75');
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- text: The sixth <code>rect</code> should have a <code>height</code> of 54.
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testString: assert($('rect').eq(5).attr('height') == '54');
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- text: The seventh <code>rect</code> should have a <code>height</code> of 87.
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testString: assert($('rect').eq(6).attr('height') == '87');
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- text: The eighth <code>rect</code> should have a <code>height</code> of 42.
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testString: assert($('rect').eq(7).attr('height') == '42');
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- text: The ninth <code>rect</code> should have a <code>height</code> of 27.
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testString: assert($('rect').eq(8).attr('height') == '27');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='html-seed'>
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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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</div>
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</section>
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## Solution
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<section id='solution'>
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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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</section>
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