92 lines
2.5 KiB
Markdown
92 lines
2.5 KiB
Markdown
|
---
|
||
|
|
id: 587d7fac367417b2b2512bdc
|
||
|
|
title: >-
|
||
|
|
Use the d3.max and d3.min Functions to Find Minimum and Maximum Values in a
|
||
|
|
Dataset
|
||
|
|
challengeType: 6
|
||
|
|
forumTopicId: 301496
|
||
|
|
dashedName: >-
|
||
|
|
use-the-d3-max-and-d3-min-functions-to-find-minimum-and-maximum-values-in-a-dataset
|
||
|
|
---
|
||
|
|
|
||
|
|
# --description--
|
||
|
|
|
||
|
|
The D3 methods `domain()` and `range()` set that information for your scale based on the data. There are a couple methods to make that easier.
|
||
|
|
|
||
|
|
Often when you set the domain, you'll want to use the minimum and maximum values within the data set. Trying to find these values manually, especially in a large data set, may cause errors.
|
||
|
|
|
||
|
|
D3 has two methods - `min()` and `max()` to return this information. Here's an example:
|
||
|
|
|
||
|
|
```js
|
||
|
|
const exampleData = [34, 234, 73, 90, 6, 52];
|
||
|
|
d3.min(exampleData)
|
||
|
|
d3.max(exampleData)
|
||
|
|
```
|
||
|
|
|
||
|
|
A dataset may have nested arrays, like the `[x, y]` coordinate pairs that were in the scatter plot example. In that case, you need to tell D3 how to calculate the maximum and minimum. Fortunately, both the `min()` and `max()` methods take a callback function. In this example, the callback function's argument `d` is for the current inner array. The callback needs to return the element from the inner array (the `x` or `y` value) over which you want to compute the maximum or minimum. Here's an example for how to find the min and max values with an array of arrays:
|
||
|
|
|
||
|
|
```js
|
||
|
|
const locationData = [[1, 7],[6, 3],[8, 3]];
|
||
|
|
const minX = d3.min(locationData, (d) => d[0]);
|
||
|
|
```
|
||
|
|
|
||
|
|
`minX` would have the value `1`.
|
||
|
|
|
||
|
|
# --instructions--
|
||
|
|
|
||
|
|
The `positionData` array holds sub arrays of x, y, and z coordinates. Use a D3 method to find the maximum value of the z coordinate (the third value) from the arrays and save it in the `output` variable.
|
||
|
|
|
||
|
|
# --hints--
|
||
|
|
|
||
|
|
The text in the `h2` should be `8`.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(output == 8 && $('h2').text() == '8');
|
||
|
|
```
|
||
|
|
|
||
|
|
Your code should use the `max()` method.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(
|
||
|
|
code.match(/\.max/g),
|
||
|
|
'Your code should use the <code>max()</code> method.'
|
||
|
|
);
|
||
|
|
```
|
||
|
|
|
||
|
|
# --seed--
|
||
|
|
|
||
|
|
## --seed-contents--
|
||
|
|
|
||
|
|
```html
|
||
|
|
<body>
|
||
|
|
<script>
|
||
|
|
const positionData = [[1, 7, -4],[6, 3, 8],[2, 9, 3]]
|
||
|
|
// Add your code below this line
|
||
|
|
|
||
|
|
const output = undefined; // Change this line
|
||
|
|
|
||
|
|
// Add your code above this line
|
||
|
|
|
||
|
|
d3.select("body")
|
||
|
|
.append("h2")
|
||
|
|
.text(output)
|
||
|
|
</script>
|
||
|
|
</body>
|
||
|
|
```
|
||
|
|
|
||
|
|
# --solutions--
|
||
|
|
|
||
|
|
```html
|
||
|
|
<body>
|
||
|
|
<script>
|
||
|
|
const positionData = [[1, 7, -4],[6, 3, 8],[2, 9, 3]]
|
||
|
|
|
||
|
|
const output = d3.max(positionData, (d) => d[2])
|
||
|
|
|
||
|
|
d3.select("body")
|
||
|
|
.append("h2")
|
||
|
|
.text(output)
|
||
|
|
</script>
|
||
|
|
</body>
|
||
|
|
```
|