Is it possible to define more than one function per file in MATLAB, and access them from outside that file?

0 votes
asked Aug 25, 2010 by nathan-fellman

When I was studying for my undergraduate degree in EE, MATLAB required each function to be defined in its own file, even if it was a one-liner.

I'm studying for a graduate degree now, and I have to write a project in MATLAB. Is this still a requirement for newer versions of MATLAB?

If it is possible to put more than one function in a file, are there any restrictions to this? For instance, can all the functions in the file be accessed from outside the file, or only the function that has the same name as the file?

Note: I am using MATLAB release R2007b.

7 Answers

0 votes
answered Aug 25, 2010 by gnovice

The first function in an m-file (i.e. the main function), is invoked when that m-file is called. It is not required that the main function have the same name as the m-file, but for clarity it should. When the function and file name differ, the file name must be used to call the main function.

All subsequent functions in the m-file, called local functions (or "subfunctions" in the older terminology), can only be called by the main function and other local functions in that m-file. Functions in other m-files can not call them.

In addition, you can also declare functions within other functions. These are called nested functions, and these can only be called from within the function they are nested. They can also have access to variables in functions in which they are nested, which makes them quite useful albeit slightly tricky to work with.

More food for thought...

There are ways around the normal function scoping behavior outlined above, such as passing function handles as output arguments as mentioned in Jonas' answer. However, I wouldn't suggest making it a habit of resorting to such tricks, as there are likely much better options for organizing your files.

For example, let's say you have a main function A in an m-file A.m, along with local functions D, E, and F. Now let's say you have two other related functions B and C in m-files B.m and C.m, respectively, that you also want to be able to call D, E, and F. Here are some options you have:

  • Put D, E, and F each in their own separate m-files, allowing any other function to call them. The downside is that the scope of these functions is large and isn't restricted to just A, B, and C, but the upside is that this is quite simple.

  • Create a defineMyFunctions m-file (like in Jonas' example) with D, E, and F as local functions and a main function that simply returns function handles to them. This allows you to keep D, E, and F in the same file, but it doesn't do anything regarding the scope of these functions since any function that can call defineMyFunctions can invoke them. You also then have to worry about passing the function handles around as arguments to make sure you have them where you need them.

  • Copy D, E and F into B.m and C.m as local functions. This limits the scope of their usage to just A, B, and C, but makes updating and maintenance of your code a nightmare because you have three copies of the same code in different places.

  • Use private functions! If you have A, B, and C in the same directory, you can create a subdirectory called private and place D, E, and F in there, each as a separate m-file. This limits their scope so they can only be called by functions in the directory immediately above (i.e. A, B, and C) and keeps them together in the same place (but still different m-files):


All this goes somewhat outside the scope of your question, and is probably more detail than you need, but I thought it might be good to touch upon the more general concern of organizing all of your m-files. ;)

0 votes
answered Aug 25, 2010 by jonas

The only way to have multiple, separately accessible functions in a single file is to define STATIC METHODS using object-oriented programming. You'd access the function as myClass.static1(), myClass.static2() etc.

OOP functionality is only officially supported since R2008a, so unless you want to use the old, undocumented OOP syntax, the answer for you is no, as explained by @gnovice.


One more way to define multiple functions inside a file that are accessible from the outside is to create a function that returns multiple function handles. In other words, you'd call your defining function as [fun1,fun2,fun3]=defineMyFunctions, after which you could use out1=fun1(inputs) etc.

0 votes
answered Aug 26, 2010 by scfrench

Generally, the answer to your question is no, you cannot define more than one externally visible function per file. You can return function handles to local functions, though, and a convenient way to do so is to make them fields of a struct. Here is an example:

function funs = makefuns

function y=fun1(x)

function z=fun2

And here is how it could be used:

>> myfuns = makefuns;
>> myfuns.fun1(5)    
ans =
>> myfuns.fun2()     
ans =
0 votes
answered Aug 1, 2013 by ru-hasha

I really like SCFrench's answer - I would like to point out that it can easily be modified to import the functions directly to the workspace using the assignin function. (Doing it like this reminds me a lot of Python's "import x from y" way of doing things)

function message = makefuns
  message='Done importing functions to workspace';

function y=fun1(x)

function z=fun2

And then used thusly:

>> makefuns
ans =
Done importing functions to workspace

>> fun1(123)
ans =

>> fun2()
ans =
0 votes
answered Aug 3, 2013 by thierry-dalon

You could also group functions in one main file together with the main function looking like this:

function [varargout] = main( subfun, varargin )
[varargout{1:nargout}] = feval( subfun, varargin{:} ); 

% paste your subfunctions below ....
function str=subfun1

Then calling subfun1 would look like this: str=main('subfun1')

0 votes
answered Aug 13, 2013 by j-d

I define multiple functions in one .m file with Octave and then use the command from within the .m file where I need to make use of the functions from that file:


Not sure if this is available with Matlab.

octave:8> help source
'source' is a built-in function

 -- Built-in Function:  source (FILE)
     Parse and execute the contents of FILE.  This is equivalent to
     executing commands from a script file, but without requiring the
     file to be named `FILE.m'.
0 votes
answered Aug 31, 2014 by smalljoeman

Along the same lines as SCFrench's answer, but with a more C# style spin..

I would (and often do) make a class containing multiple static methods. For example:

classdef Statistics

        function val = MyMean(data)
            val = mean(data);

        function val = MyStd(data)
            val = std(data);


As the methods are static you don't need to instansiate the class. You call the functions as follows:

data = 1:10;

mean = Statistics.MyMean(data);
std = Statistics.MyStd(data);     
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