Selecting Randon files from a folder tree - matlab

Question

I have this folder organization
root/folder_1/file1_1 --up to-- file_5693
root/folder_2/file2_1 --up to-- file_100
root/folder_3/file3_1 --up to-- file_600
root/folder_4/file4_1 --up to-- file_689
I'd like to select a number (1000 example) of random files in each folder and put all them together in an output folder but, for folders with less than 200 files I'd like to copy all files.
root_2/output:
file1_350
.
.
.
file2_1 --> file2_100
.
.
.
etc
how can I do this ?
I tried to list all folder names in the directory with dir command but the folder numbers are not sequential. Any help ?

Answer 1

I might misunderstand but I do not see a reason for ordering the folder names since you will copy them anyway.
The following is the script for copying files inside folders which is again is in the root directory.
You can just change the following four variables ROOT_DIR, OUT_DIR, THRESHOLD_COPY and N_RANDOM_COPY.
% Define
ROOT_DIR = './'; % where the subdirectories are located
OUT_DIR = './root2'; % copy destination
THRESHOLD_COPY = 200; % threshold for copying all files
N_RANDOM_COPY = 100; % number of files that you want to copy
dirList = dir(ROOT_DIR);
dirList = dirList(3:end); % first two are ./ and ../
dirOnlyIndicators = cell2mat({dirList.isdir});
dirs = dirList(dirOnlyIndicators);
for dirIterator = transpose(dirs)
subdirList = dir([ ROOT_DIR dirIterator.name]);
fileIndicators = ~cell2mat({subdirList.isdir});
subfileList = {subdirList(fileIndicators)};
nFiles = sum(fileIndicators);
copyIndices = [];
if nFiles > THRESHOLD_COPY
copyIndices = randperm(nFiles);
copyIndices = copyIndices(1:N_RANDOM_COPY);
else
copyIndices = 1:nFiles;
end
for copyIndex = copyIndices
copyfile([ ROOT_DIR dirIterator.name '/' subfileList{copyIndex}.name],...
[OUT_DIR '/' subfileList{copyIndex}.name],...
'f');
end
end