MATLAB Programming

Variables
Guidelines to Using Variables
Thesameguidelines that apply to MATLAB variables at the command line
also apply to variables in M-files:
• You do not need to type or declare variables used in M-files (with the
possible exception of designating them as global or persistent).
• Before assigning one variable to another, you must be sure that the variable
on the right-hand side of the assignment has a value.
• Any operation that assigns a value to a variable creates the variable, if
needed, or overwrites its current value, if it already exists.
Scope of a Variable
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 M-file scripts. Variables created at
the MATLAB command prompt can also be used by scripts without having to
declare them as global.
Functions do notusethebaseworkspace. Everyfunctionhasitsown
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 M-file have
aseparatefunction workspace.
Extending Variable Scope
In most cases, variables created within a function are known only within that
function. These variables are not available at the MATLAB command prompt
or to any other function or subfunction.
Passing Variables from Another Workspace. The most secure way to
extend the scope of a function variable is to pass it to other functions as an
argument in the function call. Since MATLAB passes data only by value,
you also need to add the variable to the return values of any function that
modifies its value.
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