Check for existence of array of files - matlab

Question

I have a cell array containing file names. I want to check for the existence of all of these files in the subject folder, and if any one does not exist I wish to send a continue to the top-most for-loop (see mock code). Is there a way to do this in a one or two liner, instead of 1) using a for-loop and a double if-statement, or 2) building a function that for-loops over exist().
subjects = {'/data/subject01','/data/subject02','/data/subject03'};
files = {'a.txt','b.txt','c.txt'};
for ii = 1:numel(subjects)
for jj = 1:numel(files)
fileExists = exist([subject{ii} '/' file{jj}],'file')
if ~fileExists
continue
end
end
if ~fileExists
continue
end
% Some code to execute if all files exist.
end

Answer 1

The *fun functions are just loops internally and are generally slower than the explicit loop. They also very often unnecessarily obfuscate the intent and behavior of the code.
You can use ismember with all and dir to make the approach clearer and remove the unnecessary loop:
subjects = {'./data/subject01','./data/subject02'};
files = {'a.txt','b.txt','c.txt'};
for ii = 1:numel(subjects)
filelist = dir(fullfile(subjects{ii}, '*.txt'));
foundfilenames = {filelist(:).name};
if all(ismember(files, foundfilenames))
fprintf('All %u files are here: %s\n', numel(files), subjects{ii})
else
fprintf('All %u files are not here: %s\n', numel(files), subjects{ii})
end
end
With my folder structure:
/data
/subject01
a.txt
b.txt
/subject02
a.txt
b.txt
c.txt
I see the following, as expected:
All 3 files are not here: ./data/subject01
All 3 files are here: ./data/subject02

Answer 2

You could remove the loop by iterating over all combinations of the two arrays:
subjects = {'/data/subject01','/data/subject02','/data/subject03'};
files = {'a.txt','b.txt','c.txt'};
a=numel(subjects);
b=numel(files);
k=a*b;
paths = arrayfun(#(ii)[subjects{mod(ii-1,a)+1} '/' files{ceil(ii/b)}],1:k,'uniformoutput',0);
checkExist = cellfun(#exist, paths, repmat({'file'},1,k));
if all(checkExist)
% Some code to execute if all files exist
end

Answer 3

Resolved it with a cellfun and by string arrays. Technically there is still a for-loop but it resolves the double if-statement. I will leave this question open for better solutions.
subjects = {'/data/subject01','/data/subject02','/data/subject03'};
files = string({'a.txt','b.txt','c.txt'});
for ii = 1:numel(subjects)
paths = subject{ii} + files;
checkExist = cellfun(#exist, cellstr(paths), repmat({'file'},size(paths))
if ~all(checkExist(:))
continue
end
% Some code to execute if all files exist.
end