Butterworth filter with matlab

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Ziko87

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Hi,
I must to design a Butterworth filter using Matlab.

Parameter:
- butterworth Highpass filter
- cut-off frequency 0.2-05 Hz
- attenuation 70\80dB

In a Workspace I have two vectors (a time vector and a data vector)

Example:
time=[0,1,2,3];
data=[32,54,65,23];
signal=plot(time, data);

Data vector contains the signal values for each instant of time (sampling frequency: 120.83 Hz).

What can I do to make the filter for this signal?
I have tried using: “butter” and using: “Toolboxes – Filter Design”.

Thank you at all.
 

hi..i never tried butterworth filter but check on the document below may be it will helpful..
**broken link removed**
best luck..
 

Hi Ziko,
I solved in this way:

fsample=120.983; %sampling frequency
rp=0.01; % Passband ripple
rs=80; % Stopband ripple
f = [0.1 0.5]; % Cutoff frequencies
a = [0 1]; % Desired amplitudes

% Compute deviations
dev = [(10^(rp/20)-1)/(10^(rp/20)+1) 10^(-rs/20)];

% Filter
[n,fo,ao,w] = firpmord(f, a, dev, fsample);
b = firpm(n,fo,ao,w);

% Data filtered
data_filtered=conv(b,data);

:idea:
 

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