I. Introduction
Time series has long been an interesting research topic, and various models have been proposed. More recently, fuzzy time-series models, which are based on fuzzy sets, have been advanced to enhance the models' forecasting capabilities and applicability. They have been favored over the conventional models because they can handle nonlinear data directly [12] and because rigid assumptions regarding the data are not needed [19]. These models have been applied to various problem domains, such as enrollment [1], [5], [6], [10], [11], [15], [17], [18], inventory [10], temperature [3], the stock index [5], [6], [8], [9], [10], [21], [22], etc., and many of them have been shown to provide better forecasting results than their conventional counterparts [1], [3], [4], [15], [17]–[19].