A rectangular baler including a bale chamber having a plurality of walls including a movable wall section, an actuator for exerting a pressure on the movable wall section, a plunger for compressing crop material, and a control system configured to control the plunger to perform cyclic plunger strokes such that in each stroke the plunger force (F) exerted by the plunger on the crop material increases to reach a maximum plunger force (Fmax) to compress a newly inserted slice of crop material. The control system includes a first module to measure, at consecutive moments during a plunger stroke, a plurality of first values for the plunger force exerted by the plunger and/or for the pressure (Pd) in the actuator; and a control module to control at least one baling setting influencing the compressing of the crop material in the bale chamber as a function of the plurality of first values.