Question

For example in testinit.m I have the following

function [x, y, m] = testinit

x=4
y=3
m=2

When I run testinit in the console it correctly displays the value. However when I type x it says

error: ‘x’ undefined…

Answer 1

The other answers are all possible solutions, but potentially more complicated than what you may be looking for. I think the first part of yuk’s answer addresses the real problem you are having, but I think it deserves a more detailed explanation…

If you have a function that has output arguments, you need to actually capture those arguments in variables when you call the function. For example, if you typed this in the Command Window:

[x, y, m] = testinit;

Then you would have your three output values present for you to use. What you were probably doing was typing this:

testinit;

This would display the values (because you didn’t end each line in the function with a semicolon to suppress displaying them), but it would not store them in variables in the Command Window for you to use later.

This is a result of how variables are stored in MATLAB, as described by the documentation on variable scope:

MATLAB stores variables in a part of memory called a workspace. The base workspace holds variables created during your interactive MATLAB session and also any variables created by running scripts. Variables created at the MATLAB command prompt can also be used by scripts without having to declare them as global.

Functions do not use the base workspace. Every function has its own function workspace. Each function workspace is kept separate from the base workspace and all other workspaces to protect the integrity of the data used by that function. Even subfunctions that are defined in the same file have a separate function workspace.

So, if you want to share variables between functions, the simplest way is to pass them back and forth via their input and output argument lists.

It should also be noted that the names you give variables in the output argument list of the function don’t have to match the names of the variables you place those output values in. For example, given this function:

function [a, b, c] = testinit
  a = 4;
  b = 3;
  c = 2;

You can make this call in the Command Window:

[x, y, m] = testinit;

And you will get x = 4, y = 3, and m = 2.