Do NOT define the callback as a character vector. The MATLAB documentation
states "Defining a callback as a character vector is not recommended". Specifying the callback with a function handle is recommended, and will make debugging your code much easier.
Do NOT use cd just to read/write data files. All MATLAB functions that read/write data files accept absolute/relative filenames: you should use fullfile to generate the absolute/relative filename and pass that to load (or whatever function you use for reading/writing data files).
Using clear is rarely required in code, and is almost always overused by beginners.
