Chapter 19: Learning Advanced Charting
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FIGURE 19.24This line chart series displays error bars based on percentage.
Adding a trendline
When you’re plotting data over time, you may want to plot a trendline that describes the data. A
trendline points out general trends in your data. In some cases, you can forecast future data with
trendlines. A single series can have more than one trendline.To add a trendline, select the data series and choose Chart Tools ➪ Layout ➪ Analysis ➪
Trendline. This drop-down control contains options for the type of trendline. The type of trendline
that you choose depends on your data. Linear trends are most common, but some data can be
described more effectively with another type.Figure 19.25 shows an XY chart with a linear trendline and the (optional) equation for the trend-
line. The trendline describes the “best fit” of the height and weight data.For more control over a trendline, right-click it and choose Format Trendline to open the Format
Trendline dialog box. One option, Moving Average, is useful for smoothing out data that has a lot
of variation (that is, “noisy” data).The Moving Average option enables you to specify the number of data points to include in each
average. For example, if you select 5, Excel averages every five data points. Figure 19.26 shows a
chart that uses a moving average trendline.