csv to fft matlab

Hello everybody,

I'm trying to convert two csv files to fft and I looked on different forums and tried a few solutions but nothing conclusive.

Someone could help me please.

Thanks

Answer 1

[Star Strider]

You cannot calculate the Fourier transfomors without a corresponding sampling frequency or time vector.

Assuming the sampling frequency is 1 kHz, try this —

files = dir('*.csv');

Fs = 1E+3;

for k = 1:numel(files)
    fn =  files(k).name;
    T{k} = readmatrix(fn);
    t{k} = linspace(0, size(T{k},1)-1, size(T{k},1)).'/Fs;
    [FTs1{k},Fv{k}] = FFT1(T{k},t{k});
    figure
    plot(t{k}, T{k})
    xlabel('Time')
    ylabel('Amplitude')
    title(fn)
    figure
    plot(Fv{k}, abs(FTs1{k})*2)
    grid
    xlabel('Frequency')
    ylabel('Magnitude')
    title(fn)
    Ax = gca;
    Ax.XScale = 'log';
end

T{1}

ans = 10000x1

-0.0456 2.3588 3.1085 3.7611 4.6293 6.3481 7.5509 8.0792 8.1042 9.3831

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T{2}

ans = 10000x1

0.0882 0.9211 1.4539 1.5864 1.8279 2.4375 2.7633 3.1545 3.7334 3.8463

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function [FTs1,Fv] = FFT1(s,t)
    t = t(:);
    L = numel(t);
    if size(s,2) == L
        s = s.';
    end
    Fs = 1/mean(diff(t));
    Fn = Fs/2;
    NFFT = 2^nextpow2(L);
    FTs = fft((s - mean(s)) .* hann(L).*ones(1,size(s,2)), NFFT)/sum(hann(L));
    Fv = Fs*(0:(NFFT/2))/NFFT;
%     Fv = linspace(0, 1, NFFT/2+1)*Fn;
    Iv = 1:numel(Fv);
    FTs1 = FTs(Iv,:);
end

EDIT — Added time-domain plots.

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[tim]

Thanks a lot for your answers !!

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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