Matlab_Codes_for_Processing/emgProcessedDataConstruction.m

% emgProcessedDataConstruction.m
% This script processes raw EMG signals from the Gait120 dataset,
% performing filtering, rectification, MVC normalization, and interpolation
% to generate processed EMG data ready for analysis.
%
% 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/
%
%---------------------------------------------------------------------------------------

clear;
clc;

subject_idx = 1;
rawdata_path = fullfile('Gait120 Data', sprintf('S%03d', subject_idx), 'EMG', 'Rawdata.mat');
rawdata = load(rawdata_path);

task_list = ["LevelWalking", "StairAscent", "StairDescent", "SlopeAscent", "SlopeDescent", "SitToStand", "StandToSit"];

emg_muscle_name_list = ["Vastus Lateralis",
                    "Rectus Femoris",
                    "Vastus Medialis",
                    "Tibialis Anterior",
                    "Biceps Femoris",
                    "Semitendinosus",
                    "Gastrocnemuis Medialis",
                    "Gastrocnemius Lateralis",
                    "Soleus Medialis",
                    "Soleus Lateralis",
                    "Peroneus Longus",
                    "Peroneus Brevis"];

task_num = length(task_list);
trajectory_fs = rawdata.Markers_info.fs;
emg_fs = rawdata.EMGs_info.fs;
emg_trajectory_fs_multiplier = emg_fs / trajectory_fs;

%% MVC EMG Data frame cutting & filtering & rectification

for task_idx = 1:task_num
    temp_task_name = task_list(task_idx);
    mvc_data_raw = rawdata.(temp_task_name).MVC_raw;
    mvc_trial_number = numel(fieldnames(mvc_data_raw));
    for mvc_idx = 1:mvc_trial_number
        temp_trial_name = sprintf("Trial%02d", mvc_idx);
        [mvc_emg_env, ~] = signalProcess(table2array(mvc_data_raw.(temp_trial_name)), emg_fs, 20, 500);
        max_time_index = min(4.5*emg_fs,length(mvc_emg_env));
        mvc_emg_env_cut = mvc_emg_env(1:max_time_index, :);
        mvc_emg_env_cut_table = array2table(mvc_emg_env_cut, "VariableNames",emg_muscle_name_list);

        subject_data_processed.(temp_task_name).MVC_envs.(temp_trial_name) = mvc_emg_env_cut_table;
    end
end

%% Task EMG Data frame cutting & filtering & rectification

for task_idx = 1:task_num
    task_name = task_list(task_idx);
    
    subject_data_processed.(task_name).nTrials = rawdata.(task_name).nTrials;
    subject_data_processed.(task_name).AvailableTrialIdx = rawdata.(task_name).AvailableTrialIdx;
    
    for trial_idx = subject_data_processed.(task_name).AvailableTrialIdx
        trial_name = sprintf("Trial%02d", trial_idx);
        temp_trial_emg = table2array(rawdata.(task_name).(trial_name).EMGs_raw);
        csv_frame_start = rawdata.(task_name).(trial_name).TotalFrame(1);
        subject_data_processed.(task_name).(trial_name).nSteps = rawdata.(task_name).(trial_name).nSteps;
        for step_idx = 1:rawdata.(task_name).(trial_name).nSteps
            step_name = sprintf("Step%02d", step_idx);
            target_frame_start = rawdata.(task_name).(trial_name).(step_name).TargetFrame(1);
            target_frame_end = rawdata.(task_name).(trial_name).(step_name).TargetFrame(2);
            target_emg_frame_start = emg_trajectory_fs_multiplier * (target_frame_start - csv_frame_start) + 1;
            target_emg_frame_end = emg_trajectory_fs_multiplier * (target_frame_end - csv_frame_start+1);
            target_emg_frame = target_emg_frame_start:target_emg_frame_end;

            [temp_task_trial_emg_env, temp_task_trial_emg_filt] = signalProcess(temp_trial_emg, emg_fs, 20, 500);
            try
                subject_data_processed.(task_name).(trial_name).(step_name).EMGs_env = array2table(temp_task_trial_emg_env(target_emg_frame,:), "VariableNames",emg_muscle_name_list);
                subject_data_processed.(task_name).(trial_name).(step_name).EMGs_filt = array2table(temp_task_trial_emg_filt(target_emg_frame,:) , "VariableNames",emg_muscle_name_list);
            catch
                fprintf("Error at %s, %s, %s\n", task_name, trial_name, step_name);
            end
        end
    end
end

%% MVC calculation

emg_device_number = 12;
trial_target_mvc_emg_list = {[1,2,3], [4], [5, 6], [7, 8, 9, 10, 11, 12], [7, 8, 9, 10, 11, 12]};

[mvc, mvc_group_num] = calculateMVC(subject_data_processed, emg_device_number, emg_fs, task_list, trial_target_mvc_emg_list);
if (mvc_group_num > 1)
    fprintf("More than one MVC at %03d subject\n", subject_idx);
end
%% EMG Normalization
for task_idx = 1:task_num
    task_name = task_list(task_idx);
    
    for trial_idx = subject_data_processed.(task_name).AvailableTrialIdx
        trial_name = sprintf("Trial%02d", trial_idx);
        for step_idx = 1:subject_data_processed.(task_name).(trial_name).nSteps
            step_name = sprintf("Step%02d", step_idx);
            temp_emg_env = subject_data_processed.(task_name).(trial_name).(step_name).EMGs_env;
            subject_data_processed.(task_name).(trial_name).(step_name).EMGs_norm = temp_emg_env./mvc(task_idx,:);
        end
    end
end
%% Normalized EMG signal interpolation
emg_spline_frame_number = 101;
for task_idx = 1:task_num
    task_name = task_list(task_idx);
    
    for trial_idx = subject_data_processed.(task_name).AvailableTrialIdx
        trial_name = sprintf("Trial%02d", trial_idx);
        subject_data_processed.(task_name).(trial_name).MVCs = mvc(task_idx,:);
        for step_idx = 1:subject_data_processed.(task_name).(trial_name).nSteps
            step_name = sprintf("Step%02d", step_idx);
            temp_emg_norm_tb = subject_data_processed.(task_name).(trial_name).(step_name).EMGs_norm;
            temp_emg_norm = table2array(temp_emg_norm_tb);
            x = linspace(0, 100, length(temp_emg_norm));
            xq = linspace(0, 100, emg_spline_frame_number);
            s = spline(x, temp_emg_norm', xq);
            interpolated_emg = array2table(s' , "VariableNames",emg_muscle_name_list);
            subject_data_processed.(task_name).(trial_name).(step_name).EMGs_interpolated = interpolated_emg;
        end
    end
end