MATLAB Programming Fundamentals - MathWorks

If you use global variables, declare them using the global keyword before you access

them within any particular location (function or command line). For example, create a

function in a file called falling.m:

function h = falling(t)

global GRAVITY

h = 1/2*GRAVITY*t.^2;

Then, enter these commands at the prompt:

global GRAVITY

GRAVITY = 32;

y = falling((0:.1:5)');

The two global statements make the value assigned to GRAVITY at the command prompt

available inside the function. However, as a more robust alternative, redefine the function

to accept the value as an input:

function h = falling(t,gravity)

h = 1/2*gravity*t.^2;

Then, enter these commands at the prompt:

GRAVITY = 32;

y = falling((0:.1:5)',GRAVITY);

Evaluating in Another Workspace

The evalin and assignin functions allow you to evaluate commands or variable names

from character vectors and specify whether to use the current or base workspace.

Like global variables, these functions carry risks of overwriting existing data. Use them

sparingly.

evalin and assignin are sometimes useful for callback functions in graphical user

interfaces to evaluate against the base workspace. For example, create a list box of

variable names from the base workspace:

function listBox

figure

lb = uicontrol('Style','listbox','Position',[10 10 100 100],...

'Callback',@update_listBox);

update_listBox(lb)

20 Function Basics