Although they seem intimidating at first glance, area graphs simply combine the features of line graphs and stacked bar graphs, and can be either two or three dimensional, with each colored segment representing a series of data. There are two types of area graphs: stacked and non-stacked. In a non-stacked graphs, each segment, representing one data series, overrides parts of another data series (3D graphs show this more clearly). For instance, in the graphs below, in 2008 the red series indicates 12 units. In stacked area graphs, however, only the visible part of each series represents the data series, so there are no overriding sections. In this case, the red series in the 2D graph below would indicate a total of 2 units in 2008 (12-10=2). This type of area graph shows the relationship of the part to the whole, and is useful if you want to examine a cumulative effect. Since distinguishing stacked from non-stacked 2D area graphs can be quite difficult, you will usually be provided with additional information that will allow you to conclude the graph type.
In these graphs, scale value grid lines are surrounding a central zero point. The numerical values can be mentioned once on one vertex, or, alternatively, each vertex can have its own values. In this instance, in 2007, operational profit was £100,000,000.
High-low-close or open-high-low-close graphs are used for displaying daily fluctuations of stock prices. It is important to be familiar with the legend conventions of these graphs, which are quite simple. In the HLC graph below, high values are marked by a triangle that intersects with the grid line, the low price is the bottom part of the line, and the close value can be inferred in this case only through a table which should accompany the graph.
In the OHLC graph below, the vertical rectangle marks the the open/close values; when the box is dark, the open value was higher than the close value. When the box is light, the open value was lower than the close value. The vertical line's edges represent the high/low values.
These graphs sometimes use different notations for marking the OHLC values, and can also include the volumes of stocks traded per day.