The a F command fits a set of data to a model formula, such as ‘y = m x + b’ where ‘m’ and ‘b’ are parameters to be determined. For a typical set of measured data there will be no single ‘m’ and ‘b’ that exactly fit the data; in this case, Calc chooses values of the parameters that provide the closest possible fit. The model formula can be entered in various ways after the key sequence a F is pressed.
If the letter P is pressed after a F but before the model description is entered, the data as well as the model formula will be plotted after the formula is determined. This will be indicated by a “P” in the minibuffer after the help message.