Sketching an area chart

In this section, we are going to use our very first example and turn it into a more stylish graph (based on the design of wind energy poster by Kristin Clute), which is an area spline chart. An area spline chart is generated using the combined properties of area and spline charts. The main data line is plotted as a spline curve and the region underneath the line is filled in a similar color with a gradient and an opaque style.

Firstly, we want to make the graph easier for viewers to look up the values for the current trend, so we move the y axis next to the latest year, that is, to the opposite side of the chart:

          yAxis: {  ....
              opposite:true
          }

The next thing is to remove the interval lines and have a thin axis line along the y axis:

          yAxis: { ....
              gridLineWidth: 0,
              lineWidth: 1,
          }

Then we simplify the y-axis title with a percentage sign and align it to the top of the axis:

            yAxis...