(1)xn=[0,1,2,3,2,1,0],程序如下：
xn=[0,1,2,3,2,1,0];
Xk=xn*exp(-j*2*pi/N).^(n'*k);
x=(Xk*exp(j*2*pi/N).^(n'*k))/N;
subplot(2,2,1);stem(n,xn);
title('x(n)');axis([-1,2*N,1.1*min(xn),1.1*max(xn
)]);
subplot(2,2,2);stem(n,abs(x));
title('IDFS|X(k)|');axis([-1,2*N,1.1*min(x),1.1*m
ax(x)]);
subplot(2,2,3),stem(k,abs(Xk));
title('|X(k)|');axis([-1,2*N,1.1*min(abs(Xk)),1.1*
max(abs(Xk))]);
subplot(2,2,4),stem(k,angle(Xk));
