Process raw data using lowpass filter

Hi,

I have a excel file with raw data containg 1200 rows and 2 columns named A and B. I'm try to apply a lowpass filter on the signal but looks like its not working, hopefully someone on here may have time to guide me to the right direction.

here is what I did so far:

imported data as a table -> created a script -> inside of the script -> load rawdata.csv

% sampling frequency [Hz]

Fs = 1000;

% sampling period [s]

Ts = 1/Fs;

% time vector [s]

t = 0:Ts:3;

% Signal A

sig_A = rawdata(:,1);

% Signal A

sig_B = rawdata(:,2);

order = 4;

fcut = 8000;

[sig_A,sig_B] = butter(order,fcut/(fs/2),'low');

x = filter(sig_A,sig_B);

Answer 1

[Alberto Mora]

You are confusing the filter coefficient with the raw signal.

Try this:

[b,a] = butter(order,fcut/(fs/2),'low');
sig_a_filt = filter(b, a, sig_A );

[nam bui]

Hello, this is the updated code I have but when I plot it, there is not any output filtered appear on the figure.

% sampling frequency [Hz]

Fs = 1000;

% sampling period [s]

Ts = 1/Fs;

% time vector [s]

t = 0:Ts:3;

% Signal A , and 1 represent for first column of raw data in the excel file

sig_A = rawdata(:,1);

% Signal A , and 2 represent for first column of raw data in the excel file

sig_B = rawdata(:,2);

order = 4;

fcut = 8000;

[a,b] = butter(order,fcut/(fs/2),'low');

x = filter(a, b, sig_A);

x1 = filter(a, b, sig_B);

plot(x,x1)

[Alberto Mora]

Please, upload also raw data.

Moreover, when you create a comment in this forum, please use the "code" section for add your code, in orther to distinguish the text to the code.

[Alberto Mora]

Here a working example.

If this helps you, please consider to accept this post as "answer", as sign of gratitude.

Fs = 1000;
Ts = 1/Fs;% sampling period [s]
t = 0:Ts:3;% time vector [s]

sig_A = sin(3*2*pi*t)+rand(size(t))*0.1-0.05;% Signal A. I just create a noisy signal...
order = 4;
fcut = 10;
[a,b] = butter(order,fcut/(Fs/2),'low');
sig_A_filt = filter(a, b, sig_A);

figure;
plot(t, sig_A); hold on
plot(t, sig_A_filt);
legend('raw signal','filtered signal')

[nam bui]

this is help, thank you and I'll accep this as anwser for sure

[Rahim Nami]

Hi everyone

Please, mathematical formula or mathematical model of the codes used. you insert

thank you

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