1. A method for determining a feedforward transfer function of a control system in a lithographic apparatus, comprising: iteratively learning a first, feedforward output signal of the control system using an iterative learning control for a first setpoint signal and a third feedforward output signal for a third setpoint signal; determining a feedforward transfer function from the first and third feedforward output signals and the first and third setpoint signals; using the feedforward transfer function to determine a second feedforward output signal for a second setpoint signal; and controlling movement of a stage using the second feedforward output signal, wherein the control system comprises a stage control system.