Figure 2

Phase portrait. (a) Two-dimensional phase portrait of almost periodic system (4.1). Time-series $x_1^{\ast }(n)$ and $x_2^{\ast }(n)$ with initial values $x_1^{\ast }(-1)=1.06$, $x_1^{\ast }(0)=1.02$, $x_2^{\ast }(-1)=0.85$, $x_2^{\ast }(0)=0.98$ for $n\in [0,100]$. (b) Three-dimensional phase portrait of almost periodic system (4.1). Time-series $x_1^{\ast }(n)$ and $x_2^{\ast }(n)$ with the above initial values for $n\in [0,100]$.