MATLAB Programming Fundamentals - MathWorks

Variables in Nested and Anonymous Functions

The scoping rules for nested and anonymous functions require that all variables used

within the function be present in the text of the code.

If you attempt to dynamically add a variable to the workspace of an anonymous function,

a nested function, or a function that contains a nested function, then MATLAB issues an

error of the form

Attempt to add variable to a static workspace.

This table describes typical operations that attempt dynamic assignment, and the

recommended ways to avoid it.

Type of Operation Best Practice to Avoid Dynamic Assignment

load Specify the variable name as an input to the

load function. Or, assign the output from the

load function to a structure array.

eval, evalin, or assignin If possible, avoid using these functions

altogether. See “Alternatives to the eval

Function” on page 2-87.

Calling a MATLAB script that creates a

variable

Convert the script to a function and pass the

variable using arguments. This approach also

clarifies the code.

Assigning to a variable in the MATLAB

debugger

Assign the variable into the base workspace,

such as

K>> assignin('base','X',myvalue)

Another way to avoid dynamic assignment is to explicitly declare the variable within the

function. For example, suppose a script named makeX.m assigns a value to variable X. A

function that calls makeX and explicitly declares X avoids the dynamic assignment error

because X is in the function workspace. A common way to declare a variable is to initialize

its value to an empty array:

function noerror

X = [];

nestedfx

function nestedfx

Variables in Nested and Anonymous Functions