Creating a built in function?

I'm sure literally everyone who doesn't know a solution to this has done exactly what I'm currently doing...

I've got a special folder on my desktop called 'Functions' where I store all my .m function files that I've written over the years and use quite often. In order to use them in various workspaces/codes I have "Change the MATLAB current folder or add its folder to the MATLAB path." Which to be fair is an acceptable solution, but I would like something a little more elegant since I often update the code to these functions but it doesn't update every copied iteration of this function.

What I would like to do is add/edit the built in functions for MATLAB so I don't have to change the workspace folder or add the function to the path! I was hoping it would be as simple as adding a folder to the C:/Program Files/MATLAB/R2020a/toolbox/matlab and adding all my functions there but I've had no such luck as it still asks me to "Change the MATLAB current folder or add its folder to the MATLAB path."

Has anyone figured out how to do this or maybe another solution? I've searched high and low in the Community Forums and Google and figured it was about time to make a post about it.

Answer 1

[dpb]

Don't put it on the Desktop, create a folder in your user area for MATLAB and then add that folder to the MATLABPATH and make permanent.

Then, do NOT make copies of these functions all over the place, you'll reference the one and only version (excepting of course, if you do have copies for various classes of inputs; there's a whole hierarchy of directory structure outlined for that purpose.

Secondly, don't even think of adding to or modifying TMW-supplied functions -- if you do that, as soon as you update you've got to do it all over again besides the confusion that ensues from having done.

If you are working on a specific project, create a working directory specifically for it and a script to move to/from that subdir and perhaps do some other housekeeping on the way...

My prototype for this purpose looks like

>> type PROJECT

function PROJECT(varargin)
% Set environment for given project work environment
% PROJ -- set working directory for PROJ data work
% Optional arguments
%   'quit' -- restore environment to normal working 
%             directory prior to initial invocation
%   'init' -- clear local persistent working directory
%             from present value for clean slate
%   'info' -- display current target data working directory
%             and present return working directory on 'QUIT'

persistent workpath
p='C:\Set\Desired\Path\String\Here';

% handle optional arguments, then quit
option=[varargin{:}];
if strncmpi(option,'init',3), clear workpath, return, end
if strncmpi(option,'info',3),
  fprintf('PROJ data location: %s\nFormer working dir: %s\n',p,workpath)
  return
end
if strncmpi(option,'quit',2), cd(workpath),return,end % restore working path

% save called-from directory if 1st invocation after 'init'
if isempty(workpath), workpath=cd; end
cd(p)             % go to working directory

I've not got fancy-enough to make it self-modifying; I have to go in and create a new one for each new project by replacing PROJECT/PROJ with appropriate names...I do generally use all caps for these and some name that is easily associated with the given project.

Between a base \work directory for run-of-the-mill sandbox, the \UTILS directory that contains my set of functions similar to yours described above, and the above for projects, I've yet to see a message about "change MATLAB folder..."

That's been over 20 years now and counting... :)

[Morgan Blankenship]

So there is no way to make that folder \UTILS and it’s functions accessible from any path without either 1. Being in the same folder or 2. Adding the folder path every time I create a new project?

[dpb]

It's ALWAYS in the path--never changes. That's invariant and set in stone...ergo, everything in it is available always without doing anything...

C:\Users\MyFirstName\Documents\MATLAB
C:\Users\MyFirstName\Documents\MATLAB\Work
C:\Users\MyFirstName\Documents\MATLAB\Utilities
C:\ML_R2019b\toolbox\matlab\capabilities
C:\ML_R2019b\toolbox\matlab\datafun
C:\ML_R2019b\toolbox\matlab\datatypes
...

is beginning of MATLABPATH on startup every session.

>> pwd
ans =
    'C:\Users\MyFirsName\Documents\MATLAB\Work'
>> 

is my default working directory -- that's where anything that is just general happens like now for the forum.

If I execute one of my project files like

>> SCCC
>> pwd
ans =
    'C:\DBNonBusiness\SCCC_Dev_Foundation\Data'
>> SCCC info
SCCC data location: C:\DBNonBusiness\SCCC_Dev_Foundation\Data
Former working dir: C:\Users\MyFirstName\Documents\MATLAB\Work
>> 

but MATLABPATH isn't changed; just the current working directory where stuff for this particular project is located.

If were building a truly major application, would probably set up a structure inside here and that could be to add to the path temporarily, but that would be set up so as to be removed again when executed

>> SCCC quit

The key point, is to emulate what TMW did -- they built a static structure of locations for the various base functions and then toolboxes and those are on the path that never needs to change. Hence they're available globally.

Do the same thing; put your utilities that are used widely in one spot and make that spot accessible globally; keep the stuff that is unique to the present workspace in its own space and work therein on that stuff--then it doesn't need to be visible globally.

[Morgan Blankenship]

Ohhhh that makes much more sense now. Thank you very much.

[dpb]

And with the userpath option that Steven points out (that I hadn't realized was there because the above has worked for me for so long had no need to change it), you could easily add an additional place or two temporarily if needed for each project.

I'll have to think about that going forward; I could probably improve factorization somewhat on some of my stuff that I've not bothered about before.

[Morgan Blankenship]

Yeah I've got several "classes" of functions in separate folders that all do similar tasks that I just haven't optimized into a single function yet out of laziness. I've used userpath before, but I didn't know that was part of the functionality!

Answer 2

[Steven Lord]

You cannot add a built-in function to MATLAB like we at MathWorks can. But you can make the MATLAB scripts, functions, and/or classes that you write accessible to MATLAB by default if you want. See the documentation page for the userpath function.

Whatever you do, I strongly recommend that you not modify any of the folders located under matlabroot and that you do not add a new folder under matlabroot, at least not unless MathWorks Support instructs you to do so or you're installing a new product or an update release.

Depending on what you're doing, perhaps making a project would be of use.

[dpb]

I built the above so long ago and just followed previous practice I wasn't even aware userpath had been introduced, Steven! :)

That makes the above easier to implement. I see it came in R2008a; in checking I see persistent came along in R2006; even before that I used a disk file to hold the working dir to do the same thing functionally...

It would have been back in mid-90s I came up w/ the above strategem.

I don't remember when TMW changed the install to create the working area in the USER folder; my recollection is that "way back when" it just used a location under the install location. Under Windows I always installed at a root level instead of the default MS penchant under "Program Files" so could have a short; easily remembered path name and particularly, get rid of the names with embedded blanks.

[Steven Lord]

persistent is older than release R2006a. [It was "Introduced before R2006a".] It's been around since at least MATLAB 5.2, release R10 (the earliest version I chose to check) and is probably older than that.

I believe you are correct that we used to create a work folder under matlabroot for users to use, but I think we realized that keeping user files there meant they might be forgotten when users install a new release and uninstall the old. Plus at least Windows tends to be protective of people writing to the Program Files areas where MATLAB is installed by default.

[dpb]

That's undoutedly so; didn't really mean to imply it had to have been then that started using persistent.

I couldn't begin to reconstruct the initial pass at the above -- I started w/ the original 3.1 Windows release and have had an install virtually continuously since.

Like many, very early on I also had a penchant to mung on TMW-supplied functions to either fix bugs or modify behavior to fit personal desires before learning that wasn't a wise way to go... :)

It was solving that problem of updating that got me started with installing upgrades into clean, version-named subdirectories which had the side benefit of having multiple versions available with the non-expiring license (other than maintenance). All of those early releases won't run now on 64-bit machine/OS, of course, but still have one older machine with a couple pretty early releases altho I finally did trash the old AST machine w/ NT and OS2 earlier this summer. Was a painful decision to come to... :)

I do recall for a few install cycles having to go and remember to make those changes to that few distribution files; by now I've forgotten just which were the key ones. I do sorta' recall there being a release by which what were bugs had been fixed and building a custom version of the one or two that preferred to operate differently that did put in the UTILS directory instead. I think even those had been relegated to the bit bucket by about R2013 or so. Somewhere there's an archive file but it's on a spare drive so not handy to refer back to, unfortunately.

Answer 3

[Morgan Blankenship]

So I have combined dpb's and Steven's answers into something that I think will change how I do my work for the better. I have tested it, but not extensively so from what I can tell it works just fine for me.

function proj(option)
% PROJECT CREATION FUNCTION
% This function allows the user to create a system of directories that
% reference back to a single directory of commonly used functions
%
% INPUTS:
%       'home' - Will send the user back to their chosen home directory
%    'newproj' - Creates a new dir and adds it to the running list of 
%                PROJECTS and adds the UTILS to the path as well
%     'update' - Goes through the list of PROJECTS and updates them to have
%                the most current version of UTILS
% OUTPUTS: None
%
% Written by: Morgan Blankenship, Ph.D. Student
%             Email - [e-mail]
% Affiliation: University of North Texas, 
%              Department of Mechanical & Energy Engineering
% Last update: July 30th, 2020

    persistent PROJECTS    
    home = 'C:\Set\Desired\Path\String\Here'; % Home directory
    UTILS = 'C:\Set\Desired\Path\String\Here'; % Directory of commonly used functions
    if strcmpi(option,'home')
        cd(home); 
    elseif strcmpi(option,'newproj')
        oldpath = pwd; 
        dir = input('Desired directory: '); 
        dirname = input('Name of directory: ');           
        cd(dir);
        addpath(genpath(UTILS));
        mkdir(dir,dirname); 
        newproj = fullfile(dir,dirname); 
        PROJECTS = [PROJECTS; newproj];  
        cd(oldpath);       
    elseif strcmpi(option,'update')
        oldpath = pwd; 
        for ii = 1:length(PROJECTS)            
            cd(PROJECTS(ii)); 
            addpath(genpath(UTILS)); 
            cd(oldpath);    
        end
    end
end

The nifty part is I found a function (genpath) that will grab all folders under the argument given. This means not only can I have psuedo-built in functions, I can also organize them into different folders like the matlabroot directory.

Thanks guys, I really appreciate your help!

[Morgan Blankenship]

Ahhh I just found a mistake. Persistent doesn't do what I thought it did. I need a way to save a list of directories to then loop through in 'update' to update the UTILS path for every Project.

[dpb]

Don't understand the problem, precisely.

persistent will save the variable content between invocations so you'll have whatever was in the variable. I use just the one location but it could be an array or whatever...even a compound structure or whatever you need it to be.

Only if you need something other than keeping the info from the initial invocation that creates the new workspace until you destroy it would you need some other type of mechanism it seems to me.

Then again, I didn't try to read your function, either... :)

[dpb]

"... to update the UTILS path for every Project."

I think there's the flaw. The UTILS location should be static and in MATLABPATH universally; there should be no need to ever update it; certainly no need to reference to get it added to a PROJECT location.

That's the point of \UTILS -- those are things you want no matter where current working directory is just as if it were a part of the TMW-distributed toolset.

I put it first so if I ever do want to refine/modify a TMW function (don't do that any more, used to be fairly frequent before a lot of the additions to base functions to add flexibility) I can alias them there and get my version first bering earlier in the search path order.

It's only stuff that is unique to the specific project that should need setting in going to the new project directory...

[Morgan Blankenship]

How do I alias TMW function because there are a lot of functions I’d like to rewrite myself? For example the factorial function, id like to reference the gamma function instead

[dpb]

You simply name your function the same and put it first in the search path.

I do NOT recommend doing this; create your functions with unique names so you don't break MATLAB compatability. Aliasing builtin or supplied functions can wreak havoc on MATLAB itself if it also relies on one of those functions for a particular behavior.

It's an easy trap to fall into when first introduced to the concept of open source of the TMW m-files or that functions alias anything and everything silently, but as the old saw on some ancient maps says "There be dragons!"

Sorry I mentioned it... :)

But, I do stand by the other advice that the UTILS directory should be static and in MATLABPATH as I illustrated above; only the variable working locations should be the modified paths that use specific locations that don't need/shouldn't have global accessibility.

IF TMW would introduce namespaces it could help a lot and also aid some in the name pollution issue the proliferation of new toolboxes and the duplicated functionality of all the similar but slightly different versions of the same thing that have exploded last few years/release cycles.