ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
145 lines
3.7 KiB
Markdown
145 lines
3.7 KiB
Markdown
---
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id: 587d7fa9367417b2b2512bd0
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title: Invert SVG Elements
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challengeType: 6
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forumTopicId: 301488
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dashedName: invert-svg-elements
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---
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# --description--
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You may have noticed the bar chart looked like it's upside-down, or inverted. This is because of how SVG uses (x, y) coordinates.
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In SVG, the origin point for the coordinates is in the upper-left corner. An `x` coordinate of 0 places a shape on the left edge of the SVG area. A `y` coordinate of 0 places a shape on the top edge of the SVG area. Higher `x` values push the rectangle to the right. Higher `y` values push the rectangle down.
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To make the bars right-side-up, you need to change the way the `y` coordinate is calculated. It needs to account for both the height of the bar and the total height of the SVG area.
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The height of the SVG area is 100. If you have a data point of 0 in the set, you would want the bar to start at the bottom of the SVG area (not the top). To do this, the `y` coordinate needs a value of 100. If the data point value were 1, you would start with a `y` coordinate of 100 to set the bar at the bottom. Then you need to account for the height of the bar of 1, so the final `y` coordinate would be 99.
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The `y` coordinate that is `y = heightOfSVG - heightOfBar` would place the bars right-side-up.
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# --instructions--
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Change the callback function for the `y` attribute to set the bars right-side-up. Remember that the `height` of the bar is 3 times the data value `d`.
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**Note**
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In general, the relationship is `y = h - m * d`, where `m` is the constant that scales the data points.
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# --hints--
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The first `rect` should have a `y` value of 64.
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```js
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assert($('rect').eq(0).attr('y') == h - dataset[0] * 3);
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```
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The second `rect` should have a `y` value of 7.
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```js
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assert($('rect').eq(1).attr('y') == h - dataset[1] * 3);
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```
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The third `rect` should have a `y` value of 34.
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```js
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assert($('rect').eq(2).attr('y') == h - dataset[2] * 3);
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```
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The fourth `rect` should have a `y` value of 49.
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```js
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assert($('rect').eq(3).attr('y') == h - dataset[3] * 3);
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```
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The fifth `rect` should have a `y` value of 25.
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```js
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assert($('rect').eq(4).attr('y') == h - dataset[4] * 3);
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```
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The sixth `rect` should have a `y` value of 46.
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```js
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assert($('rect').eq(5).attr('y') == h - dataset[5] * 3);
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```
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The seventh `rect` should have a `y` value of 13.
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```js
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assert($('rect').eq(6).attr('y') == h - dataset[6] * 3);
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```
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The eighth `rect` should have a `y` value of 58.
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```js
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assert($('rect').eq(7).attr('y') == h - dataset[7] * 3);
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```
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The ninth `rect` should have a `y` value of 73.
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```js
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assert($('rect').eq(8).attr('y') == h - dataset[8] * 3);
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```
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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", (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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.attr("width", 25)
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.attr("height", (d, i) => 3 * d);
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</script>
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</body>
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```
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# --solutions--
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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", (d, i) => h - 3 * d)
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.attr("width", 25)
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.attr("height", (d, i) => 3 * d);
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</script>
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</body>
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```
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