function_handle - Handle to function - MATLAB (original) (raw)

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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 π :
  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 _x_2 −_y_2:
  f = @(x,y) (x.^2 - y.^2);
  Anonymous functions can accept multiple inputs but return only one output.

Examples

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In a file in your current folder, create a function named cubicPoly that accepts an input to evaluate the cubic polynomial x3+x2+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)

Create the handle f to an anonymous function that evaluates the cubic polynomial x3+x2+x+1 for a given value of 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.

Extended Capabilities

Version History

Introduced before R2006a

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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. ThetimingTest 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 thetimingTest function.