When you click AutoSum Excel automatically enters a formula that uses the SUM function to sum the numbers. Select the original experiment data in Excel and then click the Scatter Scatter on the Insert tab. Trendline equation is a formula that finds a line that best fits the data points.
Add to formula with shortcut keys.
Select the new added scatter chart and then click the Trendline More Trendline Options on the Layout tab. For example you apply the formula is A1B1 in Cell C1 and it will change to F12G12 as you copy it to the Cell H12. To add the r square value to the graph click the Display R-squared value on chart check box. Sometimes we may have the requirement of extracting the trendline equation from the chart.