How to design a lowpass filter?

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Marcel345614 2021-5-4

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https://ww2.mathworks.cn/matlabcentral/answers/821135-how-to-design-a-lowpass-filter

编辑： Marcel345614 2021-5-4

I would like to filter the following data:

Obviously the data shows some oscillations with a quite constant frequency. How can I design an appropriate (low pass?) filter to filter out this noise?

(Matlab 2020b)

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Answer 1

Scott MacKenzie 2021-5-4

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https://ww2.mathworks.cn/matlabcentral/answers/821135-how-to-design-a-lowpass-filter#answer_691520

编辑：Scott MacKenzie 2021-5-4

在 MATLAB Online 中打开

You can use smoothdata as a quick-and-dirty low pass filter:

% sine wave with noise example
y1 = sin(linspace(0,20*pi,200));
y1 = y1 + rand(1,200); 
y2 = smoothdata(y1, 'movmean', 5); % through lp filter
% square wave example
y3 = repmat([1 0], 10, 10); 
y3 = y3(:);
y4 = smoothdata(y3, 'movmean', 5); % through lp filter
tiledlayout(2,2);
nexttile(1);
plot(y1);
ax = gca;
ax.YLim = [-2 2];
nexttile(3);
plot(y2);
ax = gca;
ax.YLim = [-2 2];
nexttile(2);
plot(y3);
ax = gca;
ax.YLim = [-2 2];
nexttile(4);
plot(y4);
ax = gca;
ax.YLim = [-2 2];