ABSTRACT
This chapter initially considers a polynomial regression model to analyze time series with such tendencies. The trend component model represents stochastic changes of parameters, forms a framework for modeling various types of nonstationary time series that will be introduced in succeeding chapters. However, even in the case of analyzing short-term behavior of a time series with a trend, However, a remarkable difference from the polynomial is that the trend component model can express a very flexible function globally. The chapter considers the simplest case where the time series is expressed as where w n is a white noise.
