How to import data sequentially from different folders?

Hi, I am a beginner at matlab and I'd like to make a function file to analyze data from different folders.

First, I think I should use for-loop to import data sequentially from different folders. Each .txt file was made such as "DM01/DM01_study.txt" "DM02/DM02_study.txt"..... etc. and here's my code.

It seems filenames are generated intentionally but ERROR occurs in 'importdata' line. However, there was no problem when I wrote this.

study = importdata('DM_Behaviors/DM01/DM01_study.txt')

I would really happy if I could fix this problem. Thank you in advance.

    study = dir('DM_Behaviors/DM*/*_study.txt');

    for i = 1:3
    filename = study(i).name;
    temp_data = importdata(filename);
    name = strsplit(filename, '.');
    eval(sprintf('%s=temp_data', name{1,1}));
    end

[per isakson]

Most likely the error depends on the content of the text file. We cannot help without detailed information on that file. Why not attach (paperclip button) a sample file.

See

• TUTORIAL: Why Variables Should Not Be Named Dynamically (eval)
• TUTORIAL: how to ask a question (on Answers) and get a fast answer

[Nayeon Kwon]

Thanks I've just attached the file.

[per isakson]

On R2017b

>> cac = importdata( 'DM01_study.txt' )
cac = 
  struct with fields:

            data: [37×4 double]
        textdata: {'Trial'  'ObjID'  'FB'  'RT'}
      colheaders: {'Trial'  'ObjID'  'FB'  'RT'}
  >>

works fine; no problems. What error message do you get? And what release do you use?

Try

>> cac = importdata( fullfile( study.folder, study.name) )

[Nayeon Kwon]

Yes, but it doesn't work in the for-loop. I want to read txt files one by one (sequentially). as the picture I posted, the results showed just 'filenames' not the contents of the files...

[per isakson]

"Yes, but it doesn't work in the for-loop." If you want a useful answer, you should really try to be more informative! You don't give us much of a chance to point out the mistakes you are making, e.g you didn't answer my questions: "What error message do you get? And what release do you use?".

See TUTORIAL: how to ask a question (on Answers) and get a fast answer

I've done the following experiment successfully

• Made four copies of the sample file, which you uploaded, and put them in different folders (R2017b,Win10)

>> sad = dir('h:\m\cssm\DM*\DM*.txt');
>> {sad.name}
ans =
  1×4 cell array
    {'DM01_study.txt'}    {'DM02_study.txt'}    {'DM03_study.txt'}    {'DM04_study.txt'}
>> {sad.folder}
ans =
  1×4 cell array
    {'h:\m\cssm\DM01'}    {'h:\m\cssm\DM02'}    {'h:\m\cssm\DM03'}    {'h:\m\cssm\DM04'}
>>

• run the function, cssm. (See below)

>> DM = cssm()
DM = 
  struct with fields:

      DM01_study: [1×1 struct]
      DM02_study: [1×1 struct]
      DM03_study: [1×1 struct]
      DM04_study: [1×1 struct]
  >> DM.DM04_study
  ans = 
    struct with fields:

            data: [37×4 double]
        textdata: {'Trial'  'ObjID'  'FB'  'RT'}
      colheaders: {'Trial'  'ObjID'  'FB'  'RT'}
  >>

where

function DM = cssm()
    study = dir(fullfile('h:\m\cssm\DM*\*_study.txt'));
    for jj = 1 : length( study )
        temp_data = importdata( fullfile( study(jj).folder, study(jj).name ) );
        name = strsplit( study(jj).name, '.' );
        DM.( name{1} ) = temp_data;
    end
end

I've avoided eval because of TUTORIAL: Why Variables Should Not Be Named Dynamically (eval)

[Nayeon Kwon]

Thank you very much. I got to understand how to use '(user) function' in matlab with your help.

Answer 1

[Walter Roberson]

    study = dir('DM_Behaviors/DM*/*_study.txt');
    filenames = fullfile( {study.folder}, {study.name});
    nfiles = length(filenames);
    all_data_cell = cell(nfiles, 1);
    basenames = cell(nfiles, 1);

    for K = 1 : nfiles
      filename = filenames{K};
      [~, basenames{K}, ~] = fileparts(filename);
      try
        all_data_cell{K} = readtable(filename);
      catch ME
        fprintf('Warning: problem importing file "%s"\n', filename);
        all_data_cell{K} = table();
      end
    end

   all_data = cell2struct( all_data_cell, basenames, 2 );

[Nayeon Kwon]

With a little correction, I got what I want and learned many concepts including cell/structure data types. Thank you!