The DataAccess function does not exist in file:

The error message "The DataAccess function does not exist in file:" suggests that the MATLAB interpreter is unable to find a defined function named "DataAccess" within the specified file. This can occur for several reasons:

1. **Function not defined**: Make sure that you have defined or imported the `DataAccess` function in your script or class. Check if it's at the top of the file, or if it's inside a correctly declared and accessible scope (like a function block or a class method).

2. **Typo or case sensitivity**: Double-check the spelling and capitalization of the function name, as MATLAB is case-sensitive.

3. **File path issue**: Ensure that you are referencing the correct file. If the `DataAccess.m` file is in a different directory than your current working directory or the search path, you might need to include the full path or use `addpath` to add the directory to MATLAB's search path.

4. **Function not exported**: If `DataAccess` is an internal function within a package or class, make sure it has been marked as exportable using `export` before its definition.

5. **Deleted or renamed function**: The function could have been removed from the file or accidentally renamed.

To troubleshoot further, try running this code snippet:

% Check if the function exists in the file
if exist('DataAccess', 'function')
    disp('DataAccess function found.');
else
    disp('DataAccess function not found.');
end

This will confirm whether the function is present or not.