How to creat a matrix by choosing a particular array from 100 data files.

Hi! I have 100 data files with two arrays (e.g., a_1_0, a_1_1, a_1_2, a_1_3...a_1_100.). I want to creat a matrix by choosing second array out of all 100 files, and then perform some operation.

[TADA]

I Don't Understand How The data Is Saved, Could You Post A Sample Data File?

[Abhishek Singh]

Hi there,

All of them are .dat files. So there are 100 files with the dimesnions 4000 X 2 each. I need to creat a matrix choosing the second array from each file. So the final matrix will be 4000 X 100.

Answer 1

[TADA]

Assuming those are text files formatted like you mentioned above a_x_y

you can read the second array using text scan:

xCell = textscan('text or file id', '%*s %*n %n', 'Delimiter', '_');

So now you can read the files in a loop:

folderPath = pwd;
% I assume your files are saved in a specific folder
% In that case, you can get the list with dir function
files = dir([folderPath '\*.dat']);

% preallocate matrix
A = zeros(5,length(files));

for i = 1:length(files)
    fid = fopen([files(i).folder '\' files(i).name]);
    if fid < 0
        continue;
    end
    
    % read text file, assuming the format is like you wrote a_x_y
    % This will read only the second column vector from the file
    xCell = textscan(fid, '%*s %*n %n', 'Delimiter', '_');
    
    fclose(fid);
    
    % unravel text fields cell araray 
    x = xCell{:};
    
    % If you can read just the second 
    A(:, i) = x;
end

if you have parallel computing toolbox, reading 100 files is a classic task a parfor loop