1. A printing device configured to print a diagnostic plot, the diagnostic plot comprising: a cockle pattern; a main media advance pattern; and a secondary media advance pattern; wherein the cockle pattern, main media advance pattern, and secondary media advance pattern are for providing feedback and for adjusting printing characteristics associated with the printing device; in which the cockle pattern comprises: a reference platen rule comprising a pattern representing an expected shape of the cockle pattern printed by the printing device; and a number of interference patterns each comprising a light band representing an actual cockle pattern printed by the printing device under current printing conditions.