An area chart is a graphical representation of quantitative data in the form of plotted points connected by line segments, and a color-coded region between the connected line and the x axis. These charts present 2 or more regions for comparison in a way similar to a pie chart or stacked chart.
Area charts are commonly employed for representing cumulative data over time, and in analysis of trends and related qualities. The region, or area, below the plotted line is used to represent volume. The contrasted colors allow users to easily compare large datasets.
A negative of area charts is the fact that it can be difficult to manage and view more than 2 or 3 plotted regions. Clarity is lost as the regions increase, and representing them accurately becomes awkward or impossible. The user is also forced to manipulate the time and metric ranges in strange ways to essentially bend the graph to fit its intended purpose. This limits the applications that area charts have. They may be limited to a fairly small set of practical uses, like very simple metrics that do not change in a volatile way.
There are many area chart variants. Three of the most common variants are layered, stacked area charts, and bivariate area charts. Layered area charts present 2 regions. They are layered over each other in a way that allows both to be visible. Stacked layered charts are those with multiple regions that are displayed as stacked regions. These stacked regions appear in an ascending order from bottom to top in a way that reveals the portion of the data that rises above the data below it. Bivariate area charts resemble OHLC charts. They have two plotted lines with the region between them shaded. This has the effect of expressing a range of data at a particular interval.