Issue with for loop, finding file in directory

Hi,

I'm having a problem with the code below. dirNames is a 1x14 with the names of folders with csv files in them that I need to perform calculations on. The first for loop loops through the folders. The second for loop is to loop inside each folder to read the required files. I have left out the remaining code as that part it fine.

My issue is that S is 0 (see below), and I cannot get my head around the issue.

I would appreciate any help.

for a = 1 : length(dirNames)
    fileDir = char(dirNames(a));
    
    S = dir(fullfile(fileDir,'sheet*.csv'));     % get list of data files in directory according to name structure
    S = natsortfiles(S);

    % Loop inside folder
    for k = 1:length(S)     % read data in specified sheet

Answer 1

[Voss]

You mention the file "data_1" in a comment here:

https://www.mathworks.com/matlabcentral/answers/1733090-running-4-matlab-scripts-to-read-process-and-plot-data-from-many-csv-files#comment_2195685

which makes me think possibly your files are called data_1, data_2, etc., rather than sheet*whatever.csv. If that's true, then try using data_*.csv in fullfile instead of sheet*.csv to get the set of file names to read:

for a = 1 : length(dirNames)
    fileDir = char(dirNames(a));
    
    S = dir(fullfile(fileDir,'data_*.csv'));
    S = natsortfiles(S);

    % Loop inside folder
    for k = 1:length(S)     % read data in specified sheet

On the other hand, if the files are called file1.csv, file2.csv, etc., as is stated in the question itself:

https://www.mathworks.com/matlabcentral/answers/1733090-running-4-matlab-scripts-to-read-process-and-plot-data-from-many-csv-files

Then you should use file*.csv in fullfile:

for a = 1 : length(dirNames)
    fileDir = char(dirNames(a));
    
    S = dir(fullfile(fileDir,'file*.csv'));
    S = natsortfiles(S);

    % Loop inside folder
    for k = 1:length(S)     % read data in specified sheet

The point is, you have to give fullfile the wild-card pattern that actually matches your file names.

By the way, S is not 0; it is an empty struct array (of size 0-by-1).

By the way again, you can use curly braces { } to index dirNames:

fileDir = dirNames{a};

and avoid the explicit call to char, regardless of whether dirNames is a cell array of character vectors a string array.

[ANDREW Feenan]

I have tired. I don’t think it’s a problem with the name of time files and I have changed to dirNames{a} however the second for loop still won't run.

[Voss]

Check that fileDir exists and contains the files.

Then put a breakpoint at the line

S = dir(fullfile(fileDir,'file*.csv')); % or whatever wild-card pattern is accurate

and check the same thing while the program is running. That is, check isfolder(fileDir), and check isfile(fullfile(fileDir,'file1.csv')) or whatever name of a file that you know exists in fileDir.

If all looks ok but S is still empty, post a screen shot of a directory with a set of files in it, where we can see the names of the folder and files, and post the value of your variable fileDir and/or dirNames

[ANDREW Feenan]

filedir contains the name of one of the folders, no actual .csv files.

I have set my path to the folder where the 50+ folders are located and within these 50+ folders is where the .csv files are

[Voss]

I should have said, "Check that the directory whose name is given by the value of fileDir exists, and that this directory contains the files."

What did you find when you set the breakpoint in the code and did the checks I suggested?