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

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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.

Accepted Answer

Star Strider
Star Strider on 10 Apr 2024
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.
.

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