Abstract

We study a new definition of a non-linear model of time series with hyperbolic secant function in a discrete time. The suggested model consist of two parts the first part is (linear) and the second part is (non-linear) which contains the hyperbolic secant function. We approximate this model to be linear by using the local linearization technique. We find the non-zero unique singular point that satisfies the non-linear variation equation, also stability of the non-zero unique singular point and the limit cycle if it exists of the suggested model.

Highlights

  • We study the non-linear models of time series with hyperbolic secant function

  • ‫المقترح‬ ABSTRACT We study a new definition of a non-linear model of time series with hyperbolic secant function in a discrete time

  • We find the non-zero unique singular point that satisfies the non-linear variation equation, stability of the non-zero unique singular point and the limit cycle if it exists of the suggested model

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Summary

1.Introduction

We study the non-linear models of time series with hyperbolic secant function. We find the non-zero unique singular point for the non-linear time series model with hyperbolic secant function, stability for the non-zero unique singular point and the limit cycle if it occurs. Definition 2.5: The non-linear variation (difference) equation b e xt p xt p zt , while z t is white noise and a1,..., ap ;b1,..., bp are the real constants(parameter), this model is invite as exponential autoregressive model of p order which is denoted by expAR(p) [5]. The suggested non–linear model: We will give the definition of a non-linear time series model with hyperbolic secant function of order p such as: xt [ai bi sec h(xt 1)]xt i zt (1). 2) if xt 1 0 , sec h(xt 1) 1, and the model is linear of order p p, such as: xt [ai bi ]xt i zt is linear. i 1

The stability for the suggested model
The condition of the stable unique singular point
The condition for the stable limit cycle if it exists
The stability condition of the public case of the suggested model
Examples
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