Matlab doesn't write on excel after the first loop in try catch

Hi all

I use try catch to force matlab to continue the loop and in each loop I have the parameters to write to excel files. But after the first successful loop, despite the run continues, I don't see the new files be written. Is there a reason?

[gonzalo Mier]

Without the code all the answers will be guessed. Can you provide as the code?

[farzad]

that's a problem, I can not share the code but I followed this :

link

for f = 1:size(Flist)
    
    
    
    
    try
        

        close all
        cd readfilesfolder
        filename = Flist{f};
        A = xlsread(filename);
        .....
        .....
        cd writefilesfolder
        xlswrite
        
    catch
        warning
        continue
    end
    
    mycodeagain
    
end
    
    

[Adam Danz]

@ farzad, We need a MWE. You'll need to share code that reproduces the problem. If your car doesn't start, you can't take your neighbor's car to the mechanic to get it fixed.

If your code is sensitive, you can simplify it so that it recreates the problem with as few lines as possible.

for f = 1:size(Flist)  b% <--- size(Flist) returns a 1x2 vector 
    
    try
                      
        close all
        cd readfilesfolder  %<--- it's better to use absolute paths to files 
        filename = Flist{f};        %than to change the cd within a loop
        A = xlsread(filename);  
        .....
        .....
        cd writefilesfolder % <---- see comment above
        xlswrite % <--- does it overwrite the same file each time?
        
    catch
        warning
        continue
    end
    
    mycodeagain  % <--- what's happening here?
    
end

[farzad]

Thank you very much

well I feel changing cd in the loop could be the problem , since I had many files I wanted to avoid a mess of different files in one folder.

for the last part you were asking what's happening here please look :

https://it.mathworks.com/matlabcentral/answers/413310-how-to-force-a-for-loop-to-continue

I think for the try catch continue, I should include the same code under try . Am I right ?

maybe another way is rethrow ME is it ?

[Adam Danz]

I really can't troubleshoot it without seeing the code. The link you provided is someone else's code.

"I feel changing cd in the loop could be the problem"

It certainly could lead to a problem but I doubt that this alone is preventing the loop from continuing.

If we can't see a version of your code that reproduces the problem, I recommend that you step through the code line by line in debug mode to figure out where the problem happens.

Answer 1

[Adam Danz]

Without having much information, your error is probably due to improper loop setup.

for f = 1:size(Flist)

size(Flist) probably returns a [1 x n] vector which would result in only 1 iteration of the for-loop. If Flist is a list of files you probably want

for f = 1:numel(Flist)

[farzad]

Thank you so much , I have tried it despite the f was counting to the write number anyway, I think part of the problem is due to changing folder inside the loop

[Adam Danz]

If the loop was continuing, then 'Flist" must have been a column vector or an nxm array where n>1. In any case, you don't want to use size() in that line of code. numel() is what you want.

Answer 2

[Guillaume]

There's never any reason to use cd and using cd is matlab is dangerous since it can change which m files are in scope.

It's double dangerous to use with try... catch statements if don't track which directory you are in. You may be expecting to be in the readfolder directory but are actually still in the writefolder directory, or vice-versa.

Not using cd doesn't mean you have to have everything in the same folders. You can still use as many folders as you want. All matlab functions also work with absolute paths as weel as relative paths, so the code would be something like:

readfolder = 'C:\somewehere\somefolder\toreadfrom';
writefolder = 'C:\somewhere\somefilder\towriteto';
for ...
    try
        readfile = fullfile(readfolder, Flist{f});  %build absolute path of file to read
        A = xlsread(readfile);  %A is a very poor variable name!
        ...
        writefile = fullfile(writefolder, Flist{f});  %build absolute path of file to write
        xlswrite(writefile, A);
    catch
        ...
    end
    ...
end

On a similar note, close all is also not good practice. You should track which figures you have created and close only these.