lowpassfilter seems not to work
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My lowpass filter seems to not filter, here's my code
plot(timeth,monosing,'b');
hold on
nafilter = lowpass(monosing,200,fs);
plot(timeth,nafilter,'r');
[f,P] = fourier(timeth,monosing);
[fna,Pna] = fourier(timeth,nafilter);
figure(3);
plot(f,P,'b');
hold on
plot(fna,Pna,'r');
This code should give me a lowpass filter with cutoff frequency 200 Hz but that seems to be not the case since only very high frequencies seem to have a lower amplitude in the fourier spectrum. The function fourier should work fine (already tested with other examples)
Here's the fourier spectrum graph:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/285260/image.png)
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Star Strider
2020년 4월 17일
By my calculations, the filter gives about a 15 dB attenuation. It would help to have your signal to experiment with.
Also, I assume ‘fourier’ is a function you wrote yourself. Note that it overshadows the Symbolic Math Toolbox function of the same name. That could be a problem if you want to use it symbolically.
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