matlab2

clc
n=0:100;
x=cos(pi*n/2);
k = -100:100; w = (pi/100)*k;
X = x * (exp(-j*pi/100)).^(n'*k);

magX = abs(X);angX= angle(X);
realX=real(X);imagX=imag(X);
subplot(2,2,1);plot(w/pi,magX);grid
xlabel('frequency in pi units');
title('MagnitudePart'); ylabel('Magnitude')
subplot(2,2,3);plot(w/pi,angX);grid
xlabel('frequency in pi units');
title('Angle Part'); ylabel('Radians')
subplot(2,2,2);plot(w/pi,realX);grid
xlabel('frequency in pi units');title('Real Part'); ylabel('Real')
subplot(2,2,4);plot(w/pi,imagX);grid
xlabel('frequency in pi units');
title('Imaginary Part'); ylabel('Imaginary')