Cannot create .txt file in Matlab online

I am trying to create a .txt to put some in some numbers to pull back out later.

My code is:

fileID = fopen('MyFile.txt', 'w');

When I run the code it creates a varable fileID that is shown in the workspace panel (on the lower left of the screen) as a double. But no file is created over in the files panel and when I try to read from that file it then gives an error that the file doesn't exist.

Answer 1

[Star Strider]

I am not certain what the problem is. Using fopen only creates the file ID, as you discovewred.

To write the file, you need to do something like this —

fileID = fopen('MyFile.txt', 'w');
A = magic(5)

A = 5×5

17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9

fprintf(fileID, '%2d  %2d  %2d  %2d  %2d\n', A);
fclose(fileID);

type('MyFile.txt')

17  23   4  10  11
24   5   6  12  18
 1   7  13  19  25
 8  14  20  21   2
15  16  22   3   9

That should work as well on MATLAB Online.

EDIT — (25 Sep 2023 at 15:18)

Exporting it to your computer requires that you go to MATLAB Drive, check the file name, and then click on ‘Download’. (Added in EDIT.)

.

[Stephanie]

I copied the text into the actual program once I got to a computer that had it installed. Worked perfectly. So I guess my problem was just the online platform being glitchy.

[Star Strider]

Well, no, actually. The online platform was not at all glitchy.

The fopen function creates the file identifier, and opens the file for access (reading, writing, &c.). It does nothing else. If you then want to write to the file or read from it, use the file ID to do that, with the appropriate functions, as I did here to write to it, then close the file. I just used the type function to demonstrate that it had been created and written to. I could have used readtable or readmatrix, or textscan, or fscanf to read it.

[Stephanie]

It wasn't creating a file though. I didn't show it here (though I realize now I should have) but I did have a couple fprintf lines to write info to the .txt fine and nothing was happening. There was no file, and even when I created 1 manually and uploaded it, it still wasn't being written to.

I literally changed nothing and pasted into the program and it worked, I got a file and stuff wrote to it. The only difference was the online platform vs the full program.

Regardless, now that I have access to the full program my problem seems to be resolved. I appreciate you giving some more explanation and trying to help.

[Star Strider]

Did you try your fprintf calls with my code (using them instead of my fprintf call)?

Can you try them here? (Use the Code button ‘Insert a line of code’ to format it as code and then run the code by clicking on the green Run arrow in the top toolstrip.)

I have never had any problems with MATLAB Online (that I did not cause myself).