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Why does this code fail?

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Ali Almakhmari
Ali Almakhmari on 25 Jan 2023
Commented: Ali Almakhmari on 26 Jan 2023
I have this code that looks something like the below (I cant upload the actual code). I get an error that says that: Error using fprintf Invalid File Identifier in fprintf(fid,'fgfdgfdgfd'). The weird thing is that this does not happen immediately after I run the code. The code runs smoothly and after 20 minutes of running or so I get this error. Any reasons why you would think this happen?
Edit: when I set ii, jj, kk at the ones that the code failed at and generated that error, it works just fine...I dont understand why at some point it threw that error. This is the third time I attempt running the code and it still does this.
x = 1:1:10
y = 0.1:0.01:0.2;
z = 1:0.25:3;
for ii = 1:length(x)
for jj = 1:length(y)
for kk = length(z)
fid = fopen('for1234.dat','w');
%AND THEN I RUN SOME PROCESSES using the system command

Answers (1)

VBBV on 25 Jan 2023
Edited: VBBV on 25 Jan 2023
fid = fopen('for1234.dat','w+');
Since you are writing the data repeatedly to the same file, place the above first line before all for loops and second line after all for loops.
Voss on 26 Jan 2023
Edited: Voss on 26 Jan 2023
"Should I prehaps close the file before the system command?"
Yes. If the .dat file you're writing is used by the program you're calling in the system command, and you want to create a new .dat file on each iteration of your loops (i.e., each time you call the external program), then you should open and close the .dat file like you were originally doing.
Ali Almakhmari
Ali Almakhmari on 26 Jan 2023
then if my original code that I posted was fine...why did the code fail?

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