This chart shows the amount of car travel in three metropolitan areas of California. A variable-width column chart is used to depict the interplay of two factors. Along the x-axis the existing roads are plotted in terms of lane miles. This means that for instance a 100 miles of three-line a highway add 300 lane miles. The y-axis shows how often each lane mile is traveled per day.
The product of lane miles and travel per line equals the amount if daily travel miles. If each lane of said highway section is passed by 15,000 cars per day, 4.5 million travel miles are added to the total. With variable-width chart this relationship is made clear as the width and height form the area of each element.
A line of additional data below the plotting area shows the average delay per lane mile in each area. Unsurprisingly, in densely populated areas more intensely used roads lead to higher delays.
With Aploris Charts this value is part of the chart data and can be the result from a calculation based on other chart data. This means that values and positions are automatically updated if any of the input values changes.
This type of chart is also known as a bar-mekko or skyline chart. It can be viewed as a variant of a Marimekko chart or a cross between Marimekko and column chart. In a simple application like here only one series of data is displayed while more complex application may also stack multiple series.