% 第三章: 例 3.5:
%
subplot(1,1,1)
n = 0:10; x = (0.9*exp(j*pi/3)).^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);grid
axis([-2,2,0,8])
ylabel('|X|')
title('幅度部分')
subplot(2,1,2); plot(w/pi,angX/pi);grid
axis([-2,2,-1,1])
xlabel('以pi為單位的頻率'); ylabel('弧度/pi')
title('相角部分')