error with using filter

Question

pietro 2014-9-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/155476-error-with-using-filter

编辑： Gustavo Machado 2019-6-10

采纳的回答： Honglei Chen

在 MATLAB Online 中打开

Hi all,

I have to filter few signals and I wrote the following code:

Fpass = 40;   % Passband Frequency
Fstop = 45;   % Stopband Frequency
Apass = 1;    % Passband Ripple (dB)
Astop = 80;   % Stopband Attenuation (dB)
Fs    = 100;  % Sampling Frequency
h = fdesign.lowpass('Fp,Fst,Ap,Ast', Fpass, Fstop, Apass, Astop, Fs);
Hd = design(h, 'butter','MatchExactly', 'stopband','SystemObject', true);
a=rand(1000,1);
a=filter(Hd,a);

I get the following error:

Undefined function 'filter' for input arguments of type 'dsp.BiquadFilter'.

Why do I get that error?

Thanks

Regards

Pietro

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Answer 1

Honglei Chen 2014-9-19

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https://ww2.mathworks.cn/matlabcentral/answers/155476-error-with-using-filter#answer_152287

在 MATLAB Online 中打开

dsp.BiquadFilter is a System object, so its main method is step(). Try

a = step(Hd,a)

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Gustavo Machado 2019-6-10

编辑：Gustavo Machado 2019-6-10

Honglei, I've encountered the same problem Pietro had and used step() to apply the filter, but the filter was inefficient, seems like it didn't filter the data.

I've posted a question regards my problem. I used the sosfilt(Hd.SOSMatrix) to filter my data but came across the problem described in this topic: https://www.mathworks.com/matlabcentral/answers/466353-difference-between-fvtool-filterobject-and-fvtool-filterobject-sosmatrix

I'd highly appreaciate if you could take a look at it.

Thanks in advance,

Gustavo

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