n=[-1:3];
x=1:5;
k=0:500;w=(pi/500)*k;
X=x*exp(-j*pi/500.*(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');ylabel('amplitude');
subplot(2,2,2);plot(w/pi,angX);grid;
xlabel('Frequency');ylabel('angle');
subplot(2,2,3);plot(w/pi,realX);grid;
xlabel('Frequency');ylabel('real');
subplot(2,2,4);plot(w/pi,imagX);grid;
xlabel('Frequency');ylabel('image');