x=[2,2,2,2,2,2,2,2];w=[0:1:500]*2*pi/500;
[H]=freqz(x,1,w);
magH=abs(H);phaH=angle(H);
subplot(2,2,1);plot(w/pi,magH);grid
xlabel('');ylabel('|x|');title('DTFT的幅度')
subplot(2,2,2);plot(w/pi,phaH/pi*180);grid
xlabel('以pi為單位的頻率');ylabel('度');title('DTFT的相角')
N=8;w1=2*pi/N;k=0:N-1;
X=dft(x,N);
magX=abs(X),phaX=angle(X)*180/pi
subplot(2,2,3);plot(w*N/(2*pi),magH,'--');
axis([-0.1,8.1,0,20]);
hold on
stem(k,magX);
ylabel('|x(k)|');title('DFT的幅度:N=8');text(4.3,-1,'k')
hold off
subplot(2,2,4);plot(w*N/(2*pi),phaH*180/pi,'--');
axis([-0.1,8.1,-200,200]);
hold on
stem(k,phaX);
ylabel('度');title('DFT的相角:N=8');text(4.3,-200,'k')