Hi,
The "permission denied" error occurs when the user who is running the MATLAB program does not have write permissions for the directory where the output file is being created. To fix this error, you should check the write permissions of the directory and make sure that the user running the MATLAB program has write permissions.
Here is an example code snippet that uses the dlmwrite function to write a matrix to a text file:
% Generate a matrix
A = rand(4);
% Specify the filename
filename = 'output.txt';
% Write the matrix to the file
dlmwrite(filename, A);