How to convert time domain to frequency domain using FFT

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Sanketh Shetty 2020-5-27

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https://ww2.mathworks.cn/matlabcentral/answers/534968-how-to-convert-time-domain-to-frequency-domain-using-fft

评论： Leen Mazen 2021-10-24

before test.txt

I have the data in time domain. I want to convert it into frequency domain. Can someone please provide a code for the sam? Thankyou. It will be a great help

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采纳的回答

KSSV 2020-5-27

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https://ww2.mathworks.cn/matlabcentral/answers/534968-how-to-convert-time-domain-to-frequency-domain-using-fft#answer_439883

编辑：KSSV 2020-5-27

在 MATLAB Online 中打开

data = importdata("before test.txt") ; 
t = data(:,1) ; 
amp = data(:,2) ; 
dt = unique(diff(t)) ; % time step 
Fs = 1/dt ;             % sampling frequency 
L = length(t) ; 
Y = fft(amp) ; 
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
subplot(121)
plot(t,amp) ;
xlabel('time')
ylabel('amp')
%
subplot(122)
plot(f,P1) 
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('f (Hz)')
ylabel('|P1(f)|')