One of the features in the Excel spreadsheet program from Microsoft, including the 2007 version, is the ability to create charts. Based on the data you are using, there are a variety of customizable charts to suit nearly any need. One of the ways that chats may be customized in Excel 2007 is to add a trendline to allow those who view a chart to distinguish a trend among staggered data points. You can add a trendline in Excel 2007 by following a few steps.
Select the chart to which you want to add the trendline. Click once on the data series for which you want the trendline to appear.
Click the “Add Trendline” option on the “Chart” menu. This action will open a separate pop up window.
Click the “Type” tab. Select the type of trendline that you want to add from the list of available options. Click the “OK” button to add the trendline to the chart.