Loop through ,mat files and find a specific column with conditions

I am trying to write a code to loop through 50 .mat subjects, in each subject find right and left foot, and compare three columns of left with the right foot.

If it the data in those column is similar, write a specific column, which is a matrix in a different location and save them.

But it does not read textData as matrix or rather a set of data. It reads it just as a column. Am i opening textData wrong?

%get each .mat data and routate trough it
folder=cd;
for k = 1:50
    matFilename  = sprintf('Subject%d.mat', k); % _CD_ add %d to add the number to the string
    matData      = load(fullfile(cd, matFilename)); % _CD_ matData is not used. What is it for?
    % _CD_ What is this File? Did you prepare the data before?
    fid          = fopen(fullfile(folder, matFilename), 'rt');
    textData     = fread(fid);
    
    sz = size(textData);%how many rows has the .mat data?
    L = []; %create array for left foot
    R = []; %create array for right foot
    ang = [];
    for i = 1:sz %assigne the left to an array and right as well
        if strcmp(textData(i,1) ,'LX') %find the left foot
            L = textdata(i,:);
        elseif strcmp(textData(i,1) ,'RX') %find the right foot
            R = textdata(i,:);
        end
    end
    %compaee left and right speed strideLength stepWidth
    
    szR= size(R); %size of right matrix
    szL= size(L); %size of left matrix
    for i =1:szR
        for j =1:szL 
            % if (isMatch == abs(L(i,9)-R(i,9)) < 0.1) && (isMatch == abs(L(i,10)-R(i,10)) < 0.1) && (isMatch == abs(L(i,11)-R(i,11)) < 0.1);
            if (abs(L(j,9)-R(i,9)) < 0.1) && (abs(L(j,10)-R(i,10)) < 0.1) && (abs(L(j,11)-R(i,11)) < 0.1)
                %assign the specific column and save
                rbh_bend = R(i).Ang(4,:);
                rbk_bend = R(i).Ang(7,:);
                %check if rbk_bend is negative
                % _CD_ all Values have to be inverted not only the positive ones. But because all are positive this should be no problem.
                
                rbk_bend = rbk_bend * -1;
                
                rbf_bend = R(i).Ang(10,:);
                ang(1,:) = rbh_bend;
                ang(2,:) = rbk_bend;
                ang(3,:) = rbf_bend;
                
                lbh_bend = L(j).Ang(4,:);
                lbh_bend = fliplr(lbh_bend);%flip 1-50 50-100 
                
                lbk_bend = L(j).Ang(7,:);
                % _CD_ same as above. just invert all without the if
                lbk_bend = lbk_bend * -1;
                
                lbk_bend = fliplr(lbk_bend);%flip 1-50 50-100 
                lbf_bend = L(j).Ang(10,:);
                lbf_bend = fliplr(lbf_bend);%flip 1-50 50-100 
                
                ang(4,:) = rbh_bend;
                ang(5,:) = rbk_bend;
                ang(6,:) = rbf_bend;
                
                names =  ["rbh_bend ","rbk_bend ","rbf_bend ";
                    "lbh_bend ","lbk_bend","lbf_bend "];
                File_name = sprintf(textFilename,k,i);
                save(File_name, "ang", "names") % save two different files one names and the other the %data of ang for each right and left foot with similar speed (similar three column) of each subject.
            end
        end
        
        
    end
    
    
    
    fclose(fid);
end

[Stephen23]

save(File_name, "ang", "names") % save two different files one names and the other...

Actually saves one file with two variables in it.

Getting terminology correct goes a long way to understanding what is going on.

[Niloufar Bateni]

okay, thank you. I edited it.

Answer 1

[Benjamin Thompson]

If you have MAT files you load them using the load function. No need to use fopen or fread.

[Niloufar Bateni]

Hi Benjamin,

thank you, i did that but then i get just a 1*1 result as matData, and nothing happens. It doesn't even loop through the 50 subjects. What am i doing wrong?

[Benjamin Thompson]

What is in the MAT files? If you read them successfully using fread as text, then they are not properly formatted MAT files which are binary and saved by MATLAB only. Are you trying to read text files or MAT files?

[Niloufar Bateni]

It is like a matrix with 16 columns and different number of rows.

i am trying to read the MAT file.

Actually it looks like the screenshot attached. But i need the information in Data, which is the matrix like.

But they are all .mat files.

Kind regards

[Stephen23]

As Benjamin Thompson correctly wrote, MAT files are imported using LOAD, not by fiddling with file bits.

It is strongly recommended that you LOAD into an output variable (which is a sclalar structure), e.g.:

P = 'absolute or relative path to where the files are saved';
F = sprintf('Subject%d.mat', k);
S = load(fullfile(P,F));
D = S.Data % get e.g. the DATA field

https://www.mathworks.com/help/matlab/matlab_prog/create-a-structure-array.html

Once you answer Benjamin Thompson's questions here, it will be much easier to help you. Your screenshot here appears to show 17 fields of a scalar structure, but none of those fields are anything "like a matrix with 16 columns and different number of rows", so it is unclear what you are referring to with that comment.

In any case, The code I gave above to access the DATA field of the scalar structure of the LOADed data, if that is in fact what you really have. Even better would be if you uploaded a sample data file.

[Niloufar Bateni]

Dear Stephan,

thank you, now i have the following.

%folder='/Users/nilo/Downloads/HumanMotionSimulation/Dataset';

folder = cd ;

for k = 1:50

matFilename = sprintf('Subject%d.mat', k); number to the string

matData = load(fullfile(folder, matFilename));

data = matData.s.Data; % s is the file of 17 fields of a scalar structure of which i want %to acess the Data file

update : i solved this by calling data. Foot later on.

Any idea how i can loop through data.Foot. If i got this right, Foot is one of the fileds of the data. and data is a struct.

----

in the screenshot i attached, if you click on Data in matlab you open the following photo attached (the matrix). Similar to patient.test in the link you attached. At the moment when i run the code, "data" shows the heading of the s.Data columns ( Foot

TimeStampKin

TimeStampGrf

TimeStampEmg

Task

Marker

EMG

Grf

speed

strideLength

stepWidth

cadence

Ang

Mom

Pwr

Com

).

But i want it to show the numbers and everything. So that i can access it.

later on my code is supposed to compare < speed, strideLength,stepWidth > if it is simliar between right and left foot, save Ang in a different file.

thank you and kind regards,

NIlo