Construct function handle from character vector
fh = str2func( constructs a function
fh, from a function name or text representation of an
Function handles created using
str2func do not have access to
variables outside of their local workspace or to nested functions. If your function
handle contains these variables or functions, MATLAB® throws an error when you invoke the handle. Also, if you use a text
representation of an anonymous function, the resulting function handle does not have
access to private or local functions.
Convert the character vector
'ones' to a function handle, and call the
ones function using the handle.
c = 'ones'; fh = str2func(c)
fh = function_handle with value: @ones
ans = 1×5 1 1 1 1 1
Convert a character vector that represents an anonymous
function to a function handle. Workspace variables are not available to the
str2func function. Therefore, include values in the
character vector that are necessary to evaluate the expression and that are not
defined as function inputs.
Define a character vector that represents the anonymous function 7x – 13. Convert the character vector to a function handle.
str = '@(x)7*x-13'; fh = str2func(str)
fh = @(x)7*x-13
Call the anonymous function using the handle.
ans = 8
If you include workspace variables in your character vector,
str2func creates the function handle, but MATLAB throws an error when you invoke the function handle.
a = 13; str = '@(x)7*x-a'; fh = str2func(str); fh(3)
Undefined function or variable 'a'. Error in @(x)7*x-a
Create a function that returns two function handles used to simulate the roll of dice. The first die (
d1) returns a number from 1 through 6, but the second die (
d2) always returns the number 1.
Create the following function in a folder on your MATLAB path. When
str2func is used with a character vector representing an anonymous function, it does not have access to the local function. Therefore, MATLAB calls the built-in
randi function, and returns a number from 1 through 6. The
eval function does have access to the local function, so
d2 uses the overloaded
randi and always returns 1.
function [d1,d2] = diceRoll str = '@()randi([1 6],1)'; d1 = str2func(str); d2 = eval(str); end function r = randi(~,~) r = 1; end
At the command prompt, call the
[p1,p2] = diceRoll
p1 = function_handle with value: @()randi([1,6],1) p2 = function_handle with value: @()randi([1,6],1)
p2 appear to be associated with the same anonymous function.
Invoke the function handles. The result from
p1 varies from 1 through 6. The result from
p2 is always 1.
ans = 5 ans = 1
str— Text to convert to function handle
Text to convert to a function handle, specified as a function name or a character vector or string scalar representation of an anonymous function.
str = 'cos'
str = '@(x) x.^2'
A function handle that stores variable values does not retain its original
value when you use
func2str to convert it to a character
vector, and then convert it back to a handle with
Usage notes and limitations:
The input argument must be constant/known at compile time.
Code generation does not support an input argument that represents an anonymous function.