n = [-5:5]; x = (-0.9).^n;       % x(n) = 

k = -200:200;

w = (pi/100)*k;              % [0,pi] axis divided into 101 points.

X = x * (exp(-j*pi/100)) .^ (n'*k);

magX = abs(X); angX = angle(X); realX = real(X); imagX = imag(X);

set(gcf,'Color','white');

subplot(2,2,1); plot(w/pi,magX); grid on; axis([-2,2,0,15]);

title('Magnitude Part');

xlabel('frequency in \pi units'); ylabel('Magnitude  |X|');

subplot(2,2,3); plot(w/pi, angX/pi); grid on; axis([-2,2,-1,1]);

title('Angle Part');

xlabel('frequency in \pi units'); ylabel('Radians/\pi');

subplot('2,2,2'); plot(w/pi, realX); grid on;

title('Real Part');

xlabel('frequency in \pi units'); ylabel('Real');

subplot('2,2,4'); plot(w/pi, imagX); grid on;

title('Imaginary Part');

xlabel('frequency in \pi units'); ylabel('Imaginary');