The FFT plot does not shows up, it is empty

I want to get FFT of a vibration signal that is rrecorded in csv file. Fortunately, the figure with the plot of the signal displays correct data. However, when I try to perform fft, the figure is empty. I do not know of it is because of my code, the signal (or csv), or the MATLAB settings. Could you please help me to solve the problem.

Here is the code:

data = readtable('scope_0.csv');
column2 = data.Var2;

figure;
plot(column2(1:2000));

fs = 40000;
l1 = length(column2);

fft_result = fft(column2, l1);
fft_abs = abs(fft_result);

t = 0:1/fs:2000/fs;
freq = 0 : (1/t(end)) : fs/2 - (1/t(end));

figure;
plot(freq, fft_abs(1:length(freq)));

And the figures:

[Simon Chan]

Could you restart MATLAB and try to run it again?

If it is still not successful, could you attach your data so that we can try to reproduce the same problem or not.

[Valeriya Kostyukova]

I have attached the file, thanks

Answer 1

[Star Strider]

Perhaps:

data(isinf(data)) = NaN;

data = fillmissing(data, 'linear');

since there may be a NaN or Inf value in ‘data’ that is causing the problem.

It would help to have the ‘scope_0.csv’ file.

[Valeriya Kostyukova]

Thanks, I attached the csv file

[Star Strider]

Here you go —

data = readmatrix('scope_0.csv')

data = 2002×3

NaN 1.0000 NaN NaN NaN NaN -0.0250 0.2801 NaN -0.0250 -0.1571 NaN -0.0249 -0.2727 NaN -0.0249 0.0489 NaN -0.0249 -0.0616 NaN -0.0249 0.0791 NaN -0.0249 0.5113 NaN -0.0248 -0.2526 NaN

data = readtable('scope_0.csv');
column2 = data.Var2;

column2(isinf(column2)) = NaN;
column2 = fillmissing(column2, 'linear');                   % 'fillmissing'

figure;
plot(column2(1:2000));

fs = 40000;
l1 = length(column2);

fft_result = fft(column2-mean(column2))/l1;                 % <= CHANGED (Slightly)
fft_abs = abs(fft_result);

t = 0:1/fs:2000/fs;
freq = 0 : (1/t(end)) : fs/2 - (1/t(end));

figure;
plot(freq, fft_abs(1:length(freq)));

Do not use fillmissing on ‘data’ or much (possibly all) of the matrix disappears because of the third column.

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[Valeriya Kostyukova]

thanks a lot!

[Star Strider]

My pleasure!

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

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