n=-5:5;x=(-0.9).^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,'b');grid
axis([-2,2,0,15])
xlabel('frequency in units of pi');ylabel('|X|')
title('Magnitude Part')
subplot(2,1,2),plot(w/pi,angX/pi,'b');grid
axis([-2,2,-4,4])
xlabel('frequency in unit of pi');ylabel('radians/pi')
title('Angle Part')