About line charts
A line chart displays data values as a set of points connected by a line. You typically use line charts to present large amounts of data that occur over a continuous period of time. A line chart is the most basic type of chart in finance. Figure 7-8 shows an example of a line chart, displaying the value of the Euro against the US Dollar over ten days.
A line chart is similar to an area chart, except that it does not fill in the area below the line, and it uses a square to mark each data value. There are three subtypes of line charts.
Overlay line chart
In an overlay line chart, multiple series appear as overlapping lines, as shown in Figure 7-9. The squares mark each data value. Overlay line charts show lines from each series independent of the others. The lines appear joining the values for the series.
Stacked line chart
In a stacked line chart, multiple series are stacked vertically, as shown in Figure 7-10. The stacked line chart shows totals for each series as well as the proportion that each series contributes to the grand total. In the example, the top line shows the total sales amounts for each quarter. The empty area between each line represents the sales amount for a region.
The stacked line chart is not as effective as the stacked area chart for comparing the amount that each region series contributes to the total because the areas are not shaded. In a stacked area chart, the shaded areas provide a clear visual cue that each part is compared to the whole.
In addition, as the example shows, a user can easily misinterpret the data in a stacked line chart. There is no obvious indication that the top line shows the total sales amount for each quarter and that the middle line shows the difference in the sales amount between Europe and Asia. A user viewing this chart can misinterpret the top line to represent the sales data for the U.S., the middle line to represent the sales data for Europe, and the bottom line to represent the sales data for Asia.
Figure 7-10 Stacked line chartPercent stacked line chart
A percent stacked line chart consists of multiple series stacked vertically and the values shown as a percentage of the whole. As you can see in Figure 7-11, the sales values appear as percentages instead of numbers. Like the percent stacked area chart, the percent stacked line chart makes sense only when displaying and comparing multiple series. Do not use this chart subtype if you are displaying only one series, for example, only sales for Europe.
Like the stacked line chart, the percent stacked line chart is not as effective as the percent stacked area chart.
Figure 7-11 Percent stacked line chart