I am trying to do muscle fatigue analysis, what can be done changes in the code.

with the following code i a trying to do muscle activation and fatigue analysis base on the fft values.

can someone help me with the code. what am i doing wrong and what changes can be done for the analysis

%% Import Data from TXT files
files = dir('*.txt');     % Returns all the files and folders in the directory
fileTable = struct2table(files);
numOfFiles = height(fileTable);

for k = 1:numOfFiles
    if strfind(fileTable.name{k}, 'Fatigue')
        secfiles{k} = fileTable.name{k};
    end
end
allfiles = secfiles(~cellfun(@isempty,secfiles(:,1)),:);
masterData = struct;
for j = 1:length(allfiles)
    file_info(:,j) = split(allfiles(j), "_"); 
    masterData(j).group = file_info(1,j);
    masterData(j).muscle = file_info(2,j);
    masterData(j).trial = extractBefore(file_info(4,j),'.');
    impFatigueA = importdata(allfiles(j)); 
		
		end
%%
% Fatigue Data
impFatigueA = importdata('Fatigue_A.txt');
impFatigueK = importdata('Fatigue_K.txt');
impFatigueZ = importdata('Fatigue_Z.txt');
%impMVICT2 = importdata('G2_Tricep_MVIC_2.txt');

%% Removing the DC Offset from the Signal %%

impFatigueA2 = detrend(impFatigueA); % detrend removes the mean value or linear trend from a vector or matrix. 
impFatigueK2 = detrend(impFatigueK); % detrend removes the mean value or linear trend from a vector or matrix. 
impFatigueZ2 = detrend(impFatigueZ);

 %% Rectifcication of the Signal 
 
 impFatigueA3 = abs(impFatigueA2);
 impFatigueK3 = abs(impFatigueK2);
 impFatigueZ3 = abs(impFatigueZ2);
 
 %% Creating the Envelope of the EMG Signal %%

[b,a]=butter(5,2.5/1000,'low'); % low pass filter to cut off frequency at 10Hz, using a 5th order filter and a samppling frequencyt of 1000Hz.
impFatigueA4=filtfilt(b,a,impFatigueA3);
impFatigueK4=filtfilt(b,a,impFatigueK3);
impFatigueZ4=filtfilt(b,a,impFatigueZ3);

%% fft plot for impFatigueA4 %%
Fs=1000;
L=length(impFatigueA4);
t=L/Fs;
x=impFatigueA4;
Y = fft(x);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
plot(f,P1) 
title('Frequency Spectrum Plot')
xlabel('f (Hz)')
ylabel('|P1(f)|')

Error i am getting.

Index in position 1 exceeds array bounds (must not exceed 3).

Error in untitled (line 17)
    masterData(j).trial = extractBefore(file_info(4,j),'.');
 

Answer 1

[nick]

Hi Manav,

The variable file_info is a 2x1 cell array for the "Fatigue_A.txt" stored in the zip file shared by you. As the error message implies you are trying to access an element that does not exist.

Furthermore, to import data from files using "importdata", you need to use {} to extract the filename from the files, which is a cell array (as shown in the code snippet below).

for j = 1:length(allfiles)
    file_info(:,j) = split(allfiles(j), "_"); 
    masterData(j).group = file_info(1,j);
    masterData(j).muscle = file_info(2,j);
    % masterData(j).trial = extractBefore(file_info(4,j),'.'); % The index of file_info has to change
    impFatigueA = importdata(allfiles{j}); 	
end

You may refer to the following documentation to learn more about accessing data in tables :

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

Hope this helps.