Matlab_Codes_for_Processing/signalProcess.m

function [emg_env, emg_filt] = signalProcess(emg_rawdata, fs, lowpass_coef, highpass_coef)
% signalProcess processes raw EMG signals by applying bandpass filtering,
% rectification, outlier removal, and RMS envelope extraction.
% INPUTS:
%   emg_rawdata    : Raw EMG signal data (nFrames × nEMGs)
%   fs             : EMG sampling frequency (e.g., 2000 Hz)
%   lowpass_coef   : Lower cutoff frequency for bandpass filter (Hz)
%   highpass_coef  : Upper cutoff frequency for bandpass filter (Hz)

% OUTPUTS:
%   emg_env        : Processed EMG envelope (RMS filtered signal)
%   emg_filt       : Bandpass-filtered and rectified EMG signal
%
% Author: Junyo Boo (2025)  
% Data DOI: https://doi.org/10.6084/m9.figshare.27677016  
%
% The following script is provided under the Creative Commons Attribution 4.0
% International License (CC-BY 4.0).
%
% You are free to share and adapt this material for any purpose, even commercially,
% provided you give appropriate credit, provide a link to the license, and indicate
% if changes were made. The full license text can be found at:
%
% https://creativecommons.org/licenses/by/4.0/
%
%---------------------------------------------------------------------------------------


    [b, a] = butter(2,[lowpass_coef/(fs/2) highpass_coef/(fs/2)],'bandpass');
    detrend_emg = detrend(emg_rawdata); %% zeroing
    filtered_emg = filtfilt(b,a,detrend_emg); %% bandpass filter
    rec_filtered_emg = abs(filtered_emg); %% absolute
    outlier_removed_emg = hampel(rec_filtered_emg, 250, 3); %% outlier detection
    movav_emg = sqrt(movmean(outlier_removed_emg.^2,250,1)); %% rms window
    
    visible = false;
    if visible
        figure;
        subplot(5,1,1);
        plot(emg_rawdata);
        subplot(5,1,2);
        plot(detrend_emg);
        subplot(5,1,3);
        plot(filtered_emg);
        subplot(5,1,4);
        plot(rec_filtered_emg);
        subplot(5,1,5);
        plot(movav_emg);
    end
    emg_filt = outlier_removed_emg;
    emg_env = movav_emg;
end