Call a function that is not on the Matlab path WITHOUT ADDING THAT PATH

Question

I have been searching an entire afternoon and have found no solution to call in matlab a function by specifying its path and not adding its directory to the path.

Th

Answer 1

function [varargout]=funeval(fun,varargin)
% INPUT:
% fun: (char) full path to function file
curdir=cd;
[fundir,funname]=fileparts(fun);
cd(fundir);
[varargout{1:nargout}] =feval(funname,varargin{:})
cd(curdir);

Answer 2

The run command can run a script file from any directory, but it can't call a function (with input and output arguments).

Neither feval nor str2func permit directory information in the function string.

I suggest writing your own wrapper for str2func that:

• saves the working directory
• changes directory to the script directory
• creates a function handle
• restores the original working directory

Beware, however, that a handle to a function not in the path is likely to break, because the function will be unable to invoke any helper code stored in other files in its directory.

Answer 3

I've modified Thierry Dalon's code to avoid the use of feval, which I always feel uncomfortable with. Note this still doesn't get around cd-ing to the directory in question, but well, it happens behind the scenes, so pretend it doesn't happen :-) Also note what Ben Voigt pointed out above: calls to helper functions off the path will fail.

function [varargout]=funeval(FunctionHandle, FunctionPath, varargin)
% INPUT:
% FunctionHandle: handle to the function to be called; eg @MyFunction
% FunctionPath: the path to that function
% varargin: the arguments to be passed to Myfunction
curdir=cd;
cd(FunctionPath)
[varargout{1:nargout}] = FunctionHandle(varargin{:});
cd(curdir);
end

and calling it would look like

Output = funeval(@MyFunction, 'c:\SomeDirOffMatlabsPath\', InputArgToMyFunc)

Answer 4

The solution as noted in the comment 1 to create a function handle before calling the function is nicely implemented by @Rody Oldenhuis' FEX Contribution: http://www.mathworks.com/matlabcentral/fileexchange/45941-constructor-for-functionhandles

Answer 5

This is doable, but requires a bit of parsing, and a call to evalin.

I added (many years ago!) a function to the MATLAB Central File Exchange called externalFcn

http://www.mathworks.com/matlabcentral/fileexchange/4361-externalfcn

that manages calls to off-path functions. For instance, I have a function called offpathFcn that simply returns a structure with a success message, and the value of an input. Storing that function off my MATLAB path, I can call it using:

externalfcn('out = C:\MFILES_OffPath\offpathFcn(''this is a test'')');

This returns:

out = 
    success: 1
    input: 'this is a test'

(Note that my implementation is limited, and improvable; you have to include an output with an equal sign for this to work. But it should show you how to achieve what you want.)

(MathWorks application engineer)