An apparatus for evaluating a system. The apparatus can include a storage element for receiving at least one time-varying output characteristic of the system, the time-varying output characteristic comprising a plurality of raw data points representing a plurality of measurements at a plurality of times; and a processing element communicatively coupled to the storage element. The processing element can be configured for partitioning the plurality of raw data points into a plurality of segments, calculating a plurality of estimated data points based on a plurality of mathematical expressions, and characterizing the system based on at least one figure of merit (FOM) computed from the plurality of estimated data points. In the apparatus, at least one of the plurality of mathematical expressions is associated with each of the plurality of segments.