ctl: A package for assessing agreement based on clinical tolerance limits

The ctl command implements a recently proposed statistical methodology to assess the level of agreement or interchangeability between two quantitative measurement methods. It is based on tolerance limits that are specified by the user. The methodology requires repeated measurements by at least one of the two measurement methods. It accommodates heteroskedastic measurement errors and often performs well even when the user has only one measurement by one of the two measurement methods and at least five repeated measurements from the other. It provides a more direct assessment of the agreement level than the Bland-Altman limits of agreement method and circumvents some of its deficiencies.