n=0:10;x=(0.9*exp(j*pi/3)).^n;
k=-200:200;w=(pi/100)*k;
X=x*(exp(-j*pi/100)).^(n'*k);
magX=abs(X);angX=angle(X);
subplot(2,1,1);plot(w/pi,magX);grid
xlabel('frequency in units of pi');ylabel('|X|')
title('Magnitude part')
subplot(2,1,2);plot(w/pi,angX/pi);grid
xlabel('frequency in units of pi');ylabel('radians/pi')
title('angel Part')