Indexing in a loop using fileparts

Hello,

My filenames have the timestamp in them like this: X000_104520 where the #'s after the underscore are the HH:MM:SS

I wanted to loop through the files and take only the timestamp part and save it to a table or an array.

Here is my code that I'm having some issues with the indexing of the timestamp value (TS). Any help on this is appreciated, Thank you:

fileName = dir([pwd,'\*.txt']);

for n = 1:numel(fileName)

S=6;

[~,TS(n,:)]=fileparts(fileName(n).name);

L=length(TS(n,:));

TS(n,:)=TS(n,:)(L-(S-1):L); %Not able to properly index here

Results{n} = table(TS, 'VariableNames',{sprintf('File_%d',n)});

end

Results{:}

The filenames are, as I'm not able to upload the files due to Mathworks limit?

X000_104520.txt

X001_122004.txt

X002_034536.txt

Answer 1

[Jatin]

Hi @James,

The error you're encountering is due to MATLAB not interpreting the chain of indexing, which is why attempting "TS(n,:)(L-(S-1):L)" results in an "Invalid array indexing" error. Here's a simplified version of the code that will give you the desired results.

fileName = dir([pwd,'/*.txt']);  % Get all .txt files in the current directory
TS = strings(numel(fileName), 1);  % Pre-allocate an array of strings for timestamps

for n = 1:numel(fileName)
    [~, name] = fileparts(fileName(n).name);  % Extract filename without extension
    TS(n) = name(end-5:end);  % Extract the last 6 characters for the timestamp
end

% Convert to a table and display results
Results = table(TS, 'VariableNames', {'Timestamp'});
disp(Results);

If you want to know more about the MATLAB's capacity of chained indexing, read this MATLAB Answer post:

https://www.mathworks.com/matlabcentral/answers/78242-indexing-of-fresh-array-in-one-line-without-intermediate-variable

Hope this helps!

[James]

Thank you. This works great!