xn=[7,6,5,4,3,2];
N=length(xn);
n=0:N-1;k=0:N-1;
Xk=xn*exp(-j*2*pi/N).^(n'*k);   %離散傅里葉變換
x=(Xk*exp(j*2*pi/N).^(n'*k))/N; %離散傅里葉逆變換
subplot(2,2,1),stem(n,xn,'k');
title('x(n)');axis([-1,N,1.1*min(xn),1.1*max(xn)]);
subplot(2,2,2),stem(n,abs(x),'k');   %顯示逆變換結(jié)果
title('IDFT|X(k)|');
axis([-1,N,1.1*min(x),1.1*max(x)]);
subplot(2,2,3),stem(k,abs(Xk),'k');  %顯示序列的幅度譜
title('|X(k)|');
axis([-1,N,1.1*min(abs(Xk)),1.1*max(abs(Xk))]);
subplot(2,2,4),stem(k,angle(Xk),'k');%顯示序列的相位譜
title('arg|X(k)|');
axis([-1,N,1.1*min(angle(Xk)),1.1*max(angle(Xk))]);