D3 comes alive as the *join-enter-update-remove* pattern makes legends interactive.
*Chapters*
00:00 Introduction
02:16 Cleaning up the old code
03:15 Categories and the legend
08:50 The update function
12:20 The enter function
14:50 Setting the tooltip
18:20 Making the legend interactive
*Links*
D3: Joining Data: https://d3js.org/d3-selection/joining
About the Iris Dataset: https://en.wikipedia.org/wiki/Iris_flower_data_set
An open letter to Mike Bostock: https://anthony-munnelly.com/blog/open_letter_mike_bostock/
D3 download: https://d3js.org/getting-started
Github link: https://github.com/amunnelly/d3-tutorial
