MATLAB Answers

how to use functions from private directories

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Noam Greenboim
Noam Greenboim on 7 Jun 2015
Commented: Jan on 7 Jun 2015
While I was trying to improve the performance of Excel file reading and writing, I've noticed that xlsread is using some other functions, located in a directory called ...\toolbox\matlab\iofun\private. I wrote a new function, which is composed of the code of xlsread, but it was impossible to access some functions that reside in the location above.
I tried using addpath:
addpath(fullfile(matlabroot, 'toolbox\matlab\iofun\private\'))
but I got a warning saying:
Warning: Private directories not allowed in MATLAB path
1. what's the reason for that?
2. are there any workarounds except of copying all the necessary related functions to my working directory?

Accepted Answer

Jan
Jan on 7 Jun 2015
You can have different private functions with the same name in different folders. If you inclucde such a private folder in the path, it is visible from all other functions also and then they are not "private" anymore. This can lead to ambigous dependencies and therefore it is nopt allowed.
The clean solution is to create a private folder in the folder, which contains your function, and copy the required files. Another, less clean method, is to add a wrapper function in the toolbox folder:
function varargout = myPrivateWrapperXYZ(FuncName, varargin)
[varargout(1:nargout)] = FuncName(varargin{:});
Care for a meaningful function name. This forwards all requests even to the private functions. The drawback is, that adding functions to Matlab's toolbox paths requires admin privileges and it is not portable. After a re-installation of Matlab your code will fail, and this is a bad idea in general.
  2 Comments
Jan
Jan on 7 Jun 2015
Setting the current directory to a folder of Matlab's toolbox folders can have strange side-effects. E.g. all Matlab functions, which are called implicitly will see the private functions also. But these functions are located in a private folder with the purpose, that they are not visible from the outside.

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More Answers (1)

Walter Roberson
Walter Roberson on 7 Jun 2015
Edited: Walter Roberson on 7 Jun 2015
Private functions cannot be called directly from outside routines, except by making copies of them.

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