Adding a trend line
Excel makes adding a trend line to a chart quite simple. In popup menu select Add Trendline... to display the Add Trendline dialog box.
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.
One of the options on the Trendline Options tab 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 tab enables you to specify a name to appear in the legend and the number of periods that you want to forecast. Additional options let you set the intercept value, specify that the equation used for the trend line should appear on the chart, and choose whether the R-squared value appears on the chart.
Delete a trendline
Click the trendline you want to delete and then press Delete.