how to extract data from directory

Question

sam moor 2017-1-3

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https://ww2.mathworks.cn/matlabcentral/answers/318931-how-to-extract-data-from-directory

评论： Walter Roberson 2017-1-19

I have main directory and 20 sub directories in main directory. In each sub directories there are 4 files. Now, I would like to extract those 4 files from each sub directories in matlab files so that I can do manipulation for each file without doing manually. Is there any suggestion for this?

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Answer 1

Walter Roberson 2017-1-4

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https://ww2.mathworks.cn/matlabcentral/answers/318931-how-to-extract-data-from-directory#answer_249315

在 MATLAB Online 中打开

project_dir = pwd();     %or give a particular directory name
mainDirContents = dir(project_dir);
mainDirContents(~[MainDirContents.isdir]) = [];   %remove non-folders
mask = ismember( {MainDirContents.name}, {'.', '..'} );
mainDirContents(mask) = [];                       %remove . and .. folders
num_subfolder = length(mainDirContents);
for subfold_idx= 1 : num_subfolder
  this_folder = fullfile( project_dir, mainDirContents(subfold_idx).name );
    fprintf('Now working with folder "%s"\n', this_folder );
    at2Contents = dir( fullfile(this_folder, '*.AT2') );
    num_at2 = length(at2Contents);
    for at2idx = 1 : num_at2
       this_at2 = fullfile( this_folder, at2Contents(at2idx).name );
       now do something with the file whose complete name is given by this_at2
    end
  end

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Walter Roberson 2017-1-18

在 MATLAB Online 中打开

subfolder_results = cell(num_subfolder, 1);
for subfold_idx= 1 : num_subfolder
  this_folder = fullfile( project_dir, mainDirContents(subfold_idx).name );
      fprintf('Now working with folder "%s"\n', this_folder );
      at2Contents = dir( fullfile(this_folder, '*.AT2') );
      num_at2 = length(at2Contents);
      each_file_results = cell(num_at2, 1);
      for at2idx = 1 : num_at2
         this_at2 = fullfile( this_folder, at2Contents(at2idx).name );
         now do something with the file whose complete name is given by this_at2
         each_file_results{at2idx} = the results to be saved;
      end
      subfolder_results{subfold_idx} = each_file_results;
    end

The output would be a cell array, with one element per subfolder. The cell elements would each be cell arrays with one element per file in the subfolder (the number of files per subfolder is not necessarily the same.) The results for the file would be whatever you assigned. You might want to keep track of the file name as part of the results.

In the case that you are sure that the results for one particular subfolder are all going to be numeric and the same size, you might want to do something like,

nd = ndims(each_file_results{1});
subfolder_results_as_array = cat(nd+1, each_file_results{:});

and then store that into subfolder_results{subfold_idx} instead of storing each_file_results there.

At the end, if you were sure that all of the subfolders had the same number of files and that the output for each file was numeric and exactly the same size, you could use the same kind of technique to produce an overall numeric array where the second last index was the file number within the subfolder and the last index was the subfolder number.

   nd = ndims(subfolder_results{1});
   all_results_as_array = cat(nd+1, subfolder_results{:});

Walter Roberson 2017-1-19

Are your subdirectories numbered 1 to 22? Or do they have the names given? Those names include slashes, and slashes mark directory delimiters, so you cannot be directly using those names.

Walter Roberson 2017-1-19

在 MATLAB Online 中打开

num = xlsread('NormalizationFactors.xls');
norm_factors = num(:,end);
subfolder_results = cell(num_subfolder, 1);
for subfold_idx = 1 : num_subfolder
  subfolder_name = mainDirContents(subfold_idx).name;
  this_folder = fullfile( project_dir, subfolder_name );
  fprintf('Now working with folder "%s"\n', this_folder );
    folder_id = sscanf(subfolder_name, '%d', 1);
    this_norm_value = norm_factors(folder_id);
    at2Contents = dir( fullfile(this_folder, '*.AT2') );
        num_at2 = length(at2Contents);
        each_file_results = cell(num_at2, 1);
        for at2idx = 1 : num_at2
           this_at2 = fullfile( this_folder, at2Contents(at2idx).name );
           at2_content = ReadAT2File( this_at2 );  %might as well put it inside a function
           each_file_results{at2idx} = this_norm_value * at2_content;
        end
        subfolder_results{subfold_idx} = each_file_results;
      end

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Answer 2

Geoff Hayes 2017-1-3

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https://ww2.mathworks.cn/matlabcentral/answers/318931-how-to-extract-data-from-directory#answer_249284

sam - use dir to get an array of the sub-directories (from the main directory). Then iterate over each element in this array using isdir to ensure that it is a directory. If so, then again use dir on this sub-directory to get an array of files within this sub-directory. Iterate over this array, and perform whatever manipulation that you need for the file depending upon its type. See Data Import and Export for details.

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Geoff Hayes 2017-1-3

在 MATLAB Online 中打开

What have you tried? From the main directory, use dir to grab the list of directories and files. Something like

mainDirContents = dir;

Now iterate over each element in this array and check to see if it is a directory

 for k=1:length(mainDirContents)
      if mainDirContents(k).isdir
          fprintf('dir name: %s\n',mainDirContents(k).name);
      end
 end

Depending upon your OS, you may have a couple of invalid directories that you will need to avoid. On my Mac, I would need to do

 for k=1:length(mainDirContents)
      if mainDirContents(k).isdir && ~strcmpi(mainDirContents(k).name,'.') && ~strcmpi(mainDirContents(k).name,'..')
          fprintf('dir name: %s\n',mainDirContents(k).name);
      end
 end

Now, you mention in your question that you are looking for four files but in your comment you are looking for two files. Which is it? Looking at your other question, there seems to be a bunch of files of which you are only interested in RSN953_NORTHR_MUL009.AT2 and RSN953_NORTHR_MUL279.AT2. So create the path to these files and do something with them

 for k=1:length(mainDirContents)
      if mainDirContents(k).isdir && ~strcmpi(mainDirContents(k).name,'.') && ~strcmpi(mainDirContents(k).name,'..')
          % get the path to the first file
          pathToFileA = fullfile(pwd,mainDirContents(k).name,'RSN953_NORTHR_MUL009.AT2');
          fprintf('path to file A %s\n',pathToFileA);
          % get the path to the second file
          pathToFileB = fullfile(pwd,mainDirContents(k).name,'RSN953_NORTHR_MUL279.AT2');
          fprintf('path to file B %s\n',pathToFileB);
       end
 end

What you want to do with the file is up to you...

sam moor 2017-1-3

Hi Geoff, let say If I only want to import data file having extension .AT2 from each sub folders and run a loop in every subfolders. I used fullfile but gives me error