MATLAB Answers


How to import data sequentially from different folders?

Asked by Nayeon Kwon on 15 Jun 2018
Latest activity Edited by Nayeon Kwon on 16 Jun 2018

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}));



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...

"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');
>> {}
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'}


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;

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

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

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1 Answer

Answer by Walter Roberson
on 16 Jun 2018
 Accepted Answer

    study = dir('DM_Behaviors/DM*/*_study.txt');
    filenames = fullfile( {study.folder}, {});
    nfiles = length(filenames);
    all_data_cell = cell(nfiles, 1);
    basenames = cell(nfiles, 1);
    for K = 1 : nfiles
      filename = filenames{K};
      [~, basenames{K}, ~] = fileparts(filename);
        all_data_cell{K} = readtable(filename);
      catch ME
        fprintf('Warning: problem importing file "%s"\n', filename);
        all_data_cell{K} = table();
   all_data = cell2struct( all_data_cell, basenames, 2 );

  1 Comment

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

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