n=[0:30];
a=0.9*exp(i*pi/5);
c=1;%*exp(i*pi/2);
% x(t) in complex form
x=c*(a.^n);
% amplitude of x(t)
x_abs=abs(x);
% phase of x(t);
x_phase=phase(x);
% real of x(t)
x_real=real(x);
% imaginary of x(t)
x_img=imag(x);

close all;
figure(1);

subplot(2,2,1);
stem(n,x_real);
title('real');

subplot(2,2,2);
stem(n,x_img);
title('imaginary');

subplot(2,2,3);
stem(n,x_abs);
title('amplitude');

subplot(2,2,4);
stem(n,x_phase);
title('phase');