A control system for a converting line has a sensor configured to sense a distance between the sensor and a surface of a roll of web material as the roll of web material is unwound from an unwinder and directed to the converting line. The controller is configured to: (i) determine a diameter measurement of the roll as the roll rotates based upon the sensor signals; (ii) store a plurality of data structures in a memory of a controller of a control system wherein the data structures comprise a plurality of data items associated together as the diameter measurements of the roll of the web material; (iii) process by a statistical regression analysis the data structures associated with the diameter; and (iv) generate signals for controlling the converting line based upon the processed diameter measurements.