Quote from zedDoubleNaught:
I mean, suppose you have a graph, and you can see the data points are close to a line or a curve, it will give you the formula for the line or curve that best matches it. For example, in Excel, I can plot a scatter diagram and do a linear regression to draw the best fitting line through the points. In the Excel chart, I can see the line; but then I want the app to give me the formula for that line, instead of myself having to figure out the slope and y-axis intercept and figure out the formula.
You can do this in excel. When you "activate" the regression line in the chart, you can check the "show formula" box in the menu. You have to manually type it into the spreadsheet to use it, though.