MATLAB: FFT of signal from text file

fft

Hi, I am trying to plot an FFT for an EMG signal which is saved in a text file. I did manage to plot the actual signal, but when I plotted the FFT, the window remained blank. Can someone please highlight what I am doing wrong. Also, How to determine the sampling frequency value (Fs)?
Attached please find the text file containing the EMG signal data. Thanks in advance.
Ts = mean(diff(t));                                 % Sampling Time
Fs = 1/Ts;                                          % Sampling Frequency
Fn = Fs/2;                                          % Nyquist Frequency
FEMG = fft(EMG)*2/L;                                % Fourier Transform (Normalised)
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                 % Frequency Vector
Iv = 1:length(Fv);                                  % Index Vector
figure(1)
plot(Fv, abs(FEMG(Iv)))
grid

Best Answer

I don’t see the error in your code, but the code here I wrote (plotting half of the fft) works:
fidi = fopen('John Smith emg.txt', 'rt');
T_EMG = textscan(fidi, '%f%f', 'Delimiter',' ');
t = T_EMG{1};
EMG = T_EMG{2};
L = length(t);
Ts = mean(diff(t));                                 % Sampling Time
Fs = 1/Ts;                                          % Sampling Frequency
Fn = Fs/2;                                          % Nyquist Frequency
FEMG = fft(EMG)*2/L;                                % Fourier Transform (Normalised)
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                 % Frequency Vector
Iv = 1:length(Fv);                                  % Index Vector
figure(1)
plot(Fv, abs(FEMG(Iv)))
grid
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