How to find frequency of wave data

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Marcella Roth
Marcella Roth 2021 年 3 月 18 日
編集済み: Cris LaPierre 2021 年 3 月 23 日
Hi, I have a set of data (shown below) and I would like to get the frequency of the wave Thank you!
So far I have tried:
a=readmatrix(sprintf('sampledata')) %read in data
x=a(:,2)
t= a(:,1)
z = x(t>171 & t<174.5)
zz = t(t>171 & t<174.5)
% Get sine fit
F = fit(zz, z, 'sin1');
% Plot result
plot(F,zz,z);
grid on;
xlabel('Time (secs)');
ylabel('Amplitude');
title(['Estimated frequency = ', num2str(F.b1/(2*pi)), ' Hz']);
and I get a frequnecy of 0.00075267 Hz
I can see by hand counting that the frequency is about 27-28. Any help is appreciated!

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Cris LaPierre
Cris LaPierre 2021 年 3 月 18 日
I would probably try to use findpeaks. With the right setting, you can use that to count the number of peaks. You could also do this interactively using the find local extrema live task in a live script.
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Marcella Roth
Marcella Roth 2021 年 3 月 22 日
Thank you so much for your help, I really appreciate it!

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