144 lines
3.7 KiB
Markdown
144 lines
3.7 KiB
Markdown
---
|
|
id: 587d7fa9367417b2b2512bd0
|
|
title: Invert SVG Elements
|
|
challengeType: 6
|
|
forumTopicId: 301488
|
|
dashedName: invert-svg-elements
|
|
---
|
|
|
|
# --description--
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
The `y` coordinate that is `y = heightOfSVG - heightOfBar` would place the bars right-side-up.
|
|
|
|
# --instructions--
|
|
|
|
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`.
|
|
|
|
**Note:** In general, the relationship is `y = h - m * d`, where `m` is the constant that scales the data points.
|
|
|
|
# --hints--
|
|
|
|
The first `rect` should have a `y` value of `64`.
|
|
|
|
```js
|
|
assert($('rect').eq(0).attr('y') == h - dataset[0] * 3);
|
|
```
|
|
|
|
The second `rect` should have a `y` value of `7`.
|
|
|
|
```js
|
|
assert($('rect').eq(1).attr('y') == h - dataset[1] * 3);
|
|
```
|
|
|
|
The third `rect` should have a `y` value of `34`.
|
|
|
|
```js
|
|
assert($('rect').eq(2).attr('y') == h - dataset[2] * 3);
|
|
```
|
|
|
|
The fourth `rect` should have a `y` value of `49`.
|
|
|
|
```js
|
|
assert($('rect').eq(3).attr('y') == h - dataset[3] * 3);
|
|
```
|
|
|
|
The fifth `rect` should have a `y` value of `25`.
|
|
|
|
```js
|
|
assert($('rect').eq(4).attr('y') == h - dataset[4] * 3);
|
|
```
|
|
|
|
The sixth `rect` should have a `y` value of `46`.
|
|
|
|
```js
|
|
assert($('rect').eq(5).attr('y') == h - dataset[5] * 3);
|
|
```
|
|
|
|
The seventh `rect` should have a `y` value of `13`.
|
|
|
|
```js
|
|
assert($('rect').eq(6).attr('y') == h - dataset[6] * 3);
|
|
```
|
|
|
|
The eighth `rect` should have a `y` value of `58`.
|
|
|
|
```js
|
|
assert($('rect').eq(7).attr('y') == h - dataset[7] * 3);
|
|
```
|
|
|
|
The ninth `rect` should have a `y` value of `73`.
|
|
|
|
```js
|
|
assert($('rect').eq(8).attr('y') == h - dataset[8] * 3);
|
|
```
|
|
|
|
# --seed--
|
|
|
|
## --seed-contents--
|
|
|
|
```html
|
|
<body>
|
|
<script>
|
|
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
|
|
|
|
const w = 500;
|
|
const h = 100;
|
|
|
|
const svg = d3.select("body")
|
|
.append("svg")
|
|
.attr("width", w)
|
|
.attr("height", h);
|
|
|
|
svg.selectAll("rect")
|
|
.data(dataset)
|
|
.enter()
|
|
.append("rect")
|
|
.attr("x", (d, i) => i * 30)
|
|
.attr("y", (d, i) => {
|
|
// Add your code below this line
|
|
|
|
|
|
|
|
// Add your code above this line
|
|
})
|
|
.attr("width", 25)
|
|
.attr("height", (d, i) => 3 * d);
|
|
</script>
|
|
</body>
|
|
```
|
|
|
|
# --solutions--
|
|
|
|
```html
|
|
<body>
|
|
<script>
|
|
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
|
|
|
|
const w = 500;
|
|
const h = 100;
|
|
|
|
const svg = d3.select("body")
|
|
.append("svg")
|
|
.attr("width", w)
|
|
.attr("height", h);
|
|
|
|
svg.selectAll("rect")
|
|
.data(dataset)
|
|
.enter()
|
|
.append("rect")
|
|
.attr("x", (d, i) => i * 30)
|
|
.attr("y", (d, i) => h - 3 * d)
|
|
.attr("width", 25)
|
|
.attr("height", (d, i) => 3 * d);
|
|
</script>
|
|
</body>
|
|
```
|