Motion charts: add categories and animate those bubbles

charte.ca now supports motion charts. Motion charts are basically bubble charts with one more dimension added (usually, it's time). In charte.ca, we use category for this dimension, remember category radio buttons in charte.ca pie charts and bar charts? So, our motion charts are bubble charts with category radio buttons.

Recently, Statistics Canada published a quick overview of interprovincial migration data, using simple line charts. Let's make this data look fancier:

Here are the steps to create this motion chart.