Drawing our chart
To set up our chart environment, we learn why we need two containers: wrapper and bounds.
When drawing a chart, there are two containers whose dimensions we need to define: the wrapper and the bounds.
The wrapper contains the entire chart: the data elements, the axes, the labels, etc. Every SVG element will be contained inside here.
The bounds contain all of our data elements: in this case, our line.
This distinction will help us separate the amount of space we need for extraneous elements (axes, labels), and let us focus on our main task: plotting our data. One reason this is so important to define up front is the inconsistent and unfamiliar way SVG elements are sized.