In the first article in our Charts Series, we tackled the question of when to use bar and column charts. In this new article (second in the series) let’s proceed to the similarities and differences between line charts and area charts.
Line and area charts have a similar look. In a line chart, you see a series of data points connected by line segments. An area chart has as similar look and function, but with one major difference – the area beneath each line is filled with a different color. This can present a problem: the color beneath one line can cover up some of the area beneath other lines, as well the lines themselves.
Occlusion and Number of Data Sets
A line chart is good for comparing multiple data series. Even if you plot up to seven series of data, you’ll normally still be able to understand and analyze the direction of the lines. Unfortunately the same can’t be done with an area chart, due to the occlusion factor. Data series with smaller values may be partially or completely hidden by data series with larger values, as you can see in the examples below.The occlusion issue may be minimized by adjusting color transparency. This usually works for a couple of areas, but if there are too many data series to plot, the colors will only confuse the viewers.
Part to Whole Relations
If you want to indicate the relation of a one data series (part) to the entire chart (whole), a good option is to stack the area charts. Take a look at the chart on the left below, and you’ll get an idea of the contribution of each product to the total revenue of the business for the past five years.
Stacking the area charts, however, isn’t the best move if your goal is to analyze the sales trends of each section. If you want to use past data for sales forecasts and future marketing strategies, it’s better to use a line chart, as exemplified in the chart on the right above. As you’ll notice, it’s easy to determine which products would be in high demand for the next few years.
Are you enjoying our chart series? Please be sure to come back in a week to check our next article.