Extracting phase information from FFT

Question

Jan 2013-9-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/86355-extracting-phase-information-from-fft

Hello, I wanted to know how to get phase information out of an FFT calculation like this:

NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
% Plot single-sided amplitude spectrum.
plot(f,2*abs(Y(1:NFFT/2+1))) 
title('Single-Sided Amplitude Spectrum of y(t)')
xlabel('Frequency (Hz)')
ylabel('|Y(f)|')
X=abs(Y); %takes away complex value

I understand that X gives me power information. What function or command do I need to use to extract angle information which will give me phase? Something like

angle(fft(8)) %if I want to extract phase information about freq 8Hz.

Thanks in advance for your help!