function_handle

Handle to function

Description

A function handle is a MATLAB^® data type that represents a function. A typical use of function handles is to pass a function to another function. For example, you can use function handles as input arguments to functions that evaluate mathematical expressions over a range of values. Other typical uses of function handles include:

• Specifying callback functions (for example, a callback that responds to a UI event or interacts with data acquisition hardware).

• Constructing handles to functions defined inline instead of stored in a program file (anonymous functions).

Creation

Create a function handle using the @ operator. Function handles can represent either named or anonymous functions.

• Named function handles represent functions in existing program files, including functions that are part of MATLAB and functions that you create using the function keyword. To create a handle to a named function, precede the function name with @.

  For example, create a handle to the sin function, and then use fminbnd to find the value of x that minimizes sin(x) in the range from 0 to $$2\pi$$:

  f = @sin;
  m = fminbnd(f,0,2*pi);

• Anonymous function handles (often called anonymous functions) represent single inline executable expressions that return one output. To define an anonymous function, enclose input argument names in parentheses immediately after the @ operator, and then specify the executable expression.

  For example, create a handle to an anonymous function that evaluates the expression x² − y²:

  f = @(x,y) (x.^2 - y.^2);

  Anonymous functions can accept multiple inputs but return only one output.

Examples

Find Integral of Named Function

In a file in your current folder, create a function named cubicPoly that accepts an input to evaluate the cubic polynomial ${\mathit{x}}^3+{\mathit{x}}^2+\mathit{x}+1$.

function y = cubicPoly(x)
y = x.^3 + x.^2 + x + 1; 
end

To find the integral of cubicPoly from 0 to 1, pass a handle to the cubicPoly function to integral.

q = integral(@cubicPoly,0,1)

q = 
2.0833

Find Integral of Anonymous Function

Create the handle f to an anonymous function that evaluates the cubic polynomial ${\mathit{x}}^3+{\mathit{x}}^2+\mathit{x}+1$ for a given value of $\mathit{x}$.

f = @(x) x.^3 + x.^2 + x + 1;

To find the integral of the anonymous function from 0 to 1, pass its handle to integral.

q = integral(f,0,1)

q = 
2.0833

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This datatype fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced before R2006a

R2023a: Improved performance when invoking handles to named functions

Invoking handles to named functions that are not nested shows improved performance. Invoking such function handles no longer results in an overhead compared to calling functions directly. For example, in a file named myFun.m in your current folder, create the myFun function.

function y = myFun(x)
y = x;
end

In a file named timingTest.m in your current folder, create a function that invokes a handle to myFun. The timingTest function is about 40x faster than in the previous release.

function t = timingTest
f = @myFun;
n = 1e7;
tic
for i = 1:n
    out = f(3);
end
t = toc;
end

The approximate execution times are:

R2022b: 4.4 s

R2023a: 0.11 s

The code was timed on a Windows^® 10, Intel^® Xeon^® CPU E5-1650 v4 @ 3.60 GHz test system by calling the timingTest function.