FFT 的應用有錯, 可是不知道錯再哪裡, 請幫助我, 謝謝
 

下列的程序, 老師說有錯誤, 但是我實在找不出來

老師還要我解釋 畫出的兩個圖 到底代表什麼, 我也不是很清楚
我用了註解功能, 把我想的出來的, 都寫上去了 但是不一定對
有人可以幫我一下嘛? 謝謝 真的感激不盡
我已經花了5個小時在上面了 真的 都快哭出來了

1) 找出syntax 的錯誤
2) 解釋一下這兩個 subplot 到底在建立什麼樣的模型?
橫軸座標的單位可以提供一下嗎?


謝謝



function mysteryfunction
f0 = 261.625; %frequency of the wave
harm = 3.*f0; %the harmonic is in 3 times of the fequency
npts = 8192; %2^13; it's a power of 2
freq = linspace(-1e4,1e4,npts);
cspect = zeros(size(freq)); %generate a series of 0

%10 = bandwidth;
%compute the harmonic in both positive side and negative side
lv = (abs(freq - f0)<10)|(abs(freq+f0)<10);
lv2 = (abs(freq - harm)<10)|(abs(freq+harm)<10);

cspect(lv) = 1; %define the amplitude of a specific frequency shows on the plot
cspect(lv2) = 0.25; %define the amplitude of the harmonic shows on the plot

ctime = fftshift(fft(fftshift(cspect))); %fourier transform using FFT
tt = ((-npts./2):((npts./2)-1))./2e4; %frequency span = 2e4


figure
subplot(2,1,1)
plot(freq,cspect,'-r') %shows where the two harmonics located (v.s frequency)

subplot(2,1,2)
plot(tt,real(ctime),'-r') %plot the undulation
xlim([-.02 .02])