MATLAB里用傅里叶变换求频谱

t=linspace(3,5,2048);x=t-2.5;dt=t(2)-t(1); fs=1/dt; ax=abs(fft(x)); f=(0:length(t)-1)*fs/length(t); figure(); subplot(211);plot(t,x); grid on;subplot(212);plot(f(1:25),ax(1:25));  grid on;