ip initializes the fitting parameters. If the number of parameters changes, the parameters are initialized to 5 when the fn command is executed. ip can be used at any time to change the values of the parameters. If you want to leave some parameters unchanged,enter a * in place of the number. You must enter either a number or a * for all of the parameters.
Example: ip 13.7 * 12 changes a0 to 13.7, leaves a1 the same, and changes a2 to 12 for a three parameter fit.