How can I use a function file to filter noise from an EMG signal
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I have written a script file which uses butterworth to filter my signal in the following way:
[b1,a1]=butter(5,[48/Fs*2, 52/Fs*2],'stop');
[b2,a2]=butter(5,300/Fs*2,'low');
[b3,a3]=butter(5,10/Fs*2,'high');
x = filter(b1,a1,EMG);
x1 = filter(b2,a2,x);
EMG_filtered = filter(b3,a3,x1);
This works well however as I have several different EMG signals to filter I would like to write a function which does this.
I am new to writing functions and as a first attempt tried the following:
function[EMG_filtered] = noise_removal(EMG)
Fs = 2000;
[b1,a1]=butter(5,[48/Fs*2, 52/Fs*2],'stop');
[b2,a2]=butter(5,300/Fs*2,'low');
[b3,a3]=butter(5,10/Fs*2,'high');
x = filter(b1,a1,EMG);
x1 = filter(b2,a2,x);
EMG_filtered = filter(b3,a3,x1);
This returned the error message: Undefined function 'noise_removal' for input arguments of type 'double'.
I can see the function saved in folder I am using so I dont think this is the issue.
I appreciate any help or advice
Thanks
3 Comments
Star Strider
on 23 Jun 2015
Suggestions:
You can combine the high-pass and low-pass filters into one band-pass design, saving steps in both the design and filtering.
Using the filtfilt function would prevent phase distortion that filter produces.
Answers (1)
Jan
on 23 Jun 2015
Edited: Jan
on 23 Jun 2015
3 Comments
Jan
on 23 Jun 2015
Matlab does not care about the file association of the operating system. Therefore you must have changed something else and repaired it by accident.
If the variable EMG_filtered is created inside the code, it is replied to the caller also. Either you call another version of your M-file or you did not save the file after editing. Please check:
which noise_removal -all
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