Adding a trend line

Excel makes adding a trend line to a chart quite simple. To add a trendline, select the data series and do one of the following:

• After selecting a data series, Excel displays the Chart Design and Format tabs.

  On the Chart Design tab, in the Chart Layouts group, click the Add Chart Element drop-down list:

  

  In the Add Chart Element drop-down list, choose the Trendline list:

  
• Right-click on the selected data series and select Add Trendline... in the popup menu:
  
• Click the Chart Elements button:
  

  In the Chart elements list, choose the the Trendline list:

  

The type of trend line that you choose depends on your data. Linear trends are most common, but some data can be described more effectively with another type. If necessary, you can fine-tune the trendline settings from the Format Trendline pane:

One of the options in the Trendline Options group is Moving Average, which 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.

The Trendline Options group enables you to specify a Trendline name to appear in the legend and the number of periods that you want to forecast. Set a value in the Forward and Backward fields to project your data into the future.

Additional options let you:

• Set the intercept value by selecting the Set Intercept option,
• Specify that the equation used for the trend line by selecting the Display Equation on chart option,
• Choose whether the R-squared value appears on the chart by selecting the Display R-squared value on chart option,

Delete a trendline

Click the trendline you want to delete and then press Delete.

See also this tip in French: Comment ajouter une courbe de tendance.