1. A method for determining a feature of a particular pattern, comprising: a) receiving data records, wherein at least one record of the data records includes non-stationary data; b) obtaining predetermined patterns that are associated with at least some of the data records; c) extracting particular information from at least a subset of the received data records, the particular information being indicative of the particular pattern for at least some of the data records; and d) determining whether the particular pattern is an unexpected pattern based on the obtained predetermined patterns using a processing arrangement, wherein the data records include input sequences and step (d) comprises the substeps of: i. initializing a pattern list by inserting all events of the input sequences therein, ii. scanning the input sequences to determine an interestingness measure of at least one event in the input sequences, and iii. from all patterns in the pattern list, selecting a first pattern which has a largest interestingness measure.