From bc5a2f1ee2e2890eb3cf56060577e947770b712b Mon Sep 17 00:00:00 2001
From: Matt Huntington <matt.huntington@gmail.com>
Date: Tue, 3 Oct 2017 21:30:32 -0400
Subject: [PATCH] Create an Ordinal Scale

---
 PIE.md | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/PIE.md b/PIE.md
index 1c2129d..6bf23ab 100644
--- a/PIE.md
+++ b/PIE.md
@@ -33,3 +33,23 @@ var dataset = [
     { 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]);
+mapper.domain(['Bob', 'Sally', 'Zagthor']);
+
+console.log(mapper('Bob'));
+console.log(mapper('Sally'));
+console.log(mapper('Zagthor'));
+```
+
+You cannot invert ordinal scales:
+
+```javascript
+console.log(mapper.invert(45));
+```