A method for teaching an anomaly detecting mechanism in a system comprising observable elements (302), at least one of which has a periodic time-dependent behaviour, the anomaly detecting mechanism comprising a computerized learning mechanism (314). The method comprises assembling indicators (304) indicating the behaviour of the elements (302) and arranging the assembled indicators such that each observable element's indicators are assigned to the same input data component. The learning mechanism (314) is taught so that the input data of the learning mechanism comprises the input data components which are based on the assembled indicators (304). Points which approximate the input data are placed in the input space. A presentation of time (420-424) is incorporated into at least one input data component wherein the presentation of time is periodic, continuous and un-ambiguous within the period of the at least one element with periodic time-dependent behaviour.