MATLAB Answers

Load text file from subfolder

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Hello Creative People,
I'm facing problems in loading data from subfolders. There is a main folder called "fiber optics" and this folder contains about 200k subfolders. Each subfolder contains just only one text file. How can I load text file from each subfolder one after another and plot it?

Accepted Answer

Walter Roberson
Walter Roberson on 9 Sep 2020
Edited: Walter Roberson on 9 Sep 2020
projectdir = 'fiber optics';
dinfo = dir(fullfile(projectdir, '**', '*.txt'));
filenames = fullfile({dinfo.folder}, {});
nfiles = length(filenames);
datum = cell(nfiles,1);
foldernames = cell(nfiles,1);
for K = 1 : nfiles
thisfile = filenames{K};
fullparent = fileparts(thisfile);
[~, foldername] = fileparts(fullparent);
datum{K} = load(thisfile);
foldernames{K} = foldername;
Now you have a cell array, datum, and a cell array foldernames, and can plot as appropriate, using the foldernames as labels.
I doubt that you want 200k lines on one plot, so I will not try to guess how you want to do the plotting.
Walter Roberson
Walter Roberson on 14 Sep 2020
to have it show up in the title.
Use labels{K} as the 'DisplayName' option on whatever plot() you do use, if instead you want the name to show up when you
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More Answers (1)

Adam Wyatt
Adam Wyatt on 9 Sep 2020
BaseDir = 'BaseDir'; % Change string to base folder
tmp = dir(BaseDir); % Obtains list of files and folders in BaseDir
SubDir = {}; % Extract list of names
SubDir = SubDir([tmp.isdir]); % Select entries that are directories
SubDir(1:2) = []; % Ignore first two entries ('.' and '..')
Data = cell(size(SubDir)); % Preallocate data cell array
% Loop through subfolders and perform custom load function, saving output to cell
for n=1:length(SubDir)
FullDir = fullfile(BaseDir, SubDir); % Create full folder name
fnames = dir(fullfile(FullDir, '*.txt')); % Obtain filename (assuming 'txt' extension)
Data{n} = LOAD_FUNCTION(fullfile(FullDir, fname(1).name)); % Either change LOAD_FUNCTION to built in text read function or your custom function that simply takes the filename as input
The concept is to first obtain the list of subfolders, then to loop through each subfolder and find the filename before loading it.
If the filename is the same and known in advance, you can simply use that.
If there are multiple files in the folder, you can loop through each file.
If the output is always the same size and format, you can output to a pre-allocated array rather than a cell array - I've assumed the worst-case scenario of different outputs from each file.
You need to change the BaseDir folder and the LOAD_FUNCTION function name as appropriate.

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