how to plot time and frequency domain by using FFT from CSV file?

Hi,

Hello,

I have a CSV file.How to plot time and frequency domain using Fast-Fourier Transform (FFT)?

I would be delighted to any help.

Answer 1

[Star Strider]

Try this —

A = readmatrix('FILE060.CSV');
Asz = size(A)

Asz = 1x2

729 258

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t = A(:,1);
s = A(:,2:end-1);

figure
plot(t,  s)
grid
xlim([min(A(:,1)) max(A(:,1))])
xlabel('Time (Units)')
ylabel('Amplitude (Units)')

[FTs1, Fv] = FFT1(s,t);

figure
plot(Fv, abs(FTs1)*2)
grid
xlabel('Frequency (Units)')
ylabel('Magnitude (Units)')
xlim([0 0.1])

figure
tiledlayout(4,4)
for k = 1:16:size(FTs1,2)
    nexttile
    plot(Fv, abs(FTs1(:,k))*2)
    grid
    Ax = gca;
    Ax.XMinorGrid = 'on';
    Ax.YMinorGrid = 'on';
    xlim([0 0.05])
    title("Col "+k)
end
sgtitle('Fourier Transform Array (Subset)')

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 = linspace(0, 1, NFFT/2+1)*Fn;
    Iv = 1:numel(Fv);
    FTs1 = FTs(Iv,:);
end

The complete set of 256 individual plots do not display well here, so I only plotted 16 of them individually. .

I created ‘FFT1’ for my own use, to make my life easier. Feel free to use it.

.