# Creating a Pie Chart
## Set Up
```html
```
## Set Config Vars
```javascript
var WIDTH = 360;
var HEIGHT = 360;
var radius = Math.min(WIDTH, HEIGHT) / 2;
var dataset = [
{ label: 'Abulia', count: 10 },
{ label: 'Betelgeuse', count: 20 },
{ label: 'Cantaloupe', count: 30 },
{ label: 'Dijkstra', count: 40 }
];
```
## Create an Ordinal Scale
An ordinal scale maps discrete values (can't be interpolated) to discrete values.
```javascript
var mapper = d3.scaleOrdinal();
mapper.range([45, 63, 400]); //list each value for ordinal scales, not min/max
mapper.domain(['Bob', 'Sally', 'Zagthor']); //list each value for ordinal scales, not min/max
console.log(mapper('Bob'));
console.log(mapper('Sally'));
console.log(mapper('Zagthor'));
```
You cannot invert ordinal scales:
```javascript
console.log(mapper.invert(45));
```
## Create the color scale to map labels to colors
D3 comes with lots of pre-made color schemes:
- https://github.com/d3/d3-scale/blob/master/README.md#category-scales
- https://github.com/d3/d3-scale-chromatic#categorical
They're just arrays:
```javascript
console.log(d3.schemeCategory10)
```
Consequently, we can use them when setting a range:
```javascript
var colorScale = d3.scaleOrdinal();
colorScale.range(d3.schemeCategory10);
```
We can generate an array of labels for the domain using JavaScript's map function:
```javascript
colorScale.domain(dataset.map(function(element){
return element.label;
}));
```
## Set up the svg
Standard:
```javascript
d3.select('svg')
.attr('width', WIDTH)
.attr('height', HEIGHT);
```