How to loop through a folder?
Show older comments
I currently have 24 folders within a folder and I was wondering if it was possible to loop through the 24 folders and extract information from a subfolder within the 24 folders.
1 Comment
Brando Miranda
on 30 Mar 2018
great question. This is some of the trivialest things to do in a language and its incomprehensible how hard it is to do in matlab.
Answers (3)
Image Analyst
on 11 Mar 2014
4 votes
See my attached demo where it recurses through a folder and all subfolders.
13 Comments
N
on 11 Jun 2014
hi I love your code. I do have a question with it. If I would like to save the fullFileName, so it doesn't get overwritten every time, how would i do it?
Image Analyst
on 11 Jun 2014
Make it a cell array
fullFileName{counter} = fullfile(thisFolder, baseFileNames(f).name);
counter = counter + 1;
N
on 11 Jun 2014
If I do this, I get the error:
Cell contents assignment to a non-cell array object.
Image Analyst
on 11 Jun 2014
Worked fine for me. See attachment.
N
on 14 Jun 2014
thanks it works for me now too !
Mor H
on 4 Jul 2016
Thanks a lot !
Arantza Dobbels
on 6 Jul 2016
Hey guys! this is exactly the code that I need but for some reason when I try to run it, it says the number of folders is 1 and then says that there are no files in the subfolders. What am I doing wrong? Thanks!
Vanessa Machuca
on 16 Jun 2017
Edited: Vanessa Machuca
on 16 Jun 2017
I'm facing the same issue as Arantza. :(
Image Analyst
on 16 Jun 2017
I made a newer one to use the new capabilities of dir() to use to recurse into subfolders. Try it. It's attached. Works for Release R2016b and later.
Brando Miranda
on 20 Dec 2017
do you a non recursive version?
Image Analyst
on 20 Dec 2017
Not sure what you're looking for. The program itself is not recursive - it uses the standard capability of the built-in dir() function. What I meant by recursive is that it finds files in folder, and in subfolders of those folder, and in subfolders of those subfolders, etc. until you've reached the deepest level of the directory tree.
What kind of problem are you having with the program such that you wanted to ask that question?
Rik
on 10 Dec 2020
You can use the ** option of dir. What did you try?
Image Analyst
on 10 Dec 2020
Yes, essentially it's
filePattern = sprintf('%s/**/*.*', topLevelFolder);
allFileInfo = dir(filePattern);
See my attached m-file for a full demo with tons of explanations.
Sean de Wolski
on 11 Mar 2014
Edited: Sean de Wolski
on 11 Mar 2014
You can use the dir command to give you the names and then loop over them.
files = dir;
directoryNames = {files([files.isdir]).name};
directoryNames = directoryNames(~ismember(directoryNames,{'.','..'}))
Now run the for-loop over directoryNames and apply your analysis to each
7 Comments
andrew
on 11 Mar 2014
Sean de Wolski
on 11 Mar 2014
Loop over the directory and use a wildcard inside of dir to grab all of the csv files. Something like
dir([directory '\*.csv'])
andrew
on 11 Mar 2014
Edited: Walter Roberson
on 11 Mar 2014
Walter Roberson
on 11 Mar 2014
Note: fullfile() is better practice than concatenating file substrings.
And if you were to construct the specification as a variable you could then
ls(TheVariable)
to see if the files are found that way.
Brando Miranda
on 30 Mar 2018
why does
directories_names_list = dir('noise*')
for expt_dir = directories_names_list.name
not work?
Brando Miranda
on 30 Mar 2018
why does
directoryNames = {files([files.isdir]).name};
work? its really cryptic? are u using list comprehensions or what dark magic is going on there?
@Brando Miranda: "list comprehensions" exist only in Python. They do not exist in MATLAB.
manideep reddy
on 18 Apr 2018
see my code below but make sure that the folder which we are looping through contains only flolders and not files.
cd pwd ; ## Or any other working directory you want
X = ls ;
disp(X) ;
for itr = 1:size(X)(1)
string_1 = X(itr,:) ;
string_2{itr} = deblank(string_1) ; ## This deletes the trailing blank spaces
end
for itr = 1:size(X)(1)
cd(string_2{itr})
cd ../
# DO SOMETHING #
end
end2 Comments
This code has several bugs and could be significantly improved:
- Do NOT use cd. Using cd is slower than using absolute/relative filepaths, makes debugging more difficult, and changes which functions/scripts are accessible to MATLAB. It is NOT necessary to cd directories where datafiles are stored because all MATLAB filereading/writing functions accept relative/absolute paths. Basically cd should only be used interactively, and NOT used in code. See:
- Do NOT use ls for parsing filenames. This operator is intended for displaying a list in the command window, but parsing its output char array is a waste of time. dir is what the MATLAB documentation recommends and shows in all examples that require reading multiple files from a folder, e.g.:
- size(X)(1) is not valid MATLAB syntax, and will throw an error.
- string_2 is not preallocated.
- A loop is anyway not required for deblanking the filenames: simply use deblank(cellstr(X)).
Rather than following this buggy code, I recommend that other users follow the examples shown in the MATLAB help and wiki:
manideep reddy
on 20 Apr 2018
Thank you very much. I am actually not a computer science student. So, just answered the query without considering algorithm and complexity. Anyway, I will implement your suggestions/ recommendations in future. Thanks..!
Categories
Find more on File Operations in Help Center and File Exchange
on 10 Dec 2020
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
