Create Function Handle - MATLAB & Simulink - MathWorks Deutschland (2024)

What Is a Function Handle?

A function handle is a MATLAB^® data type that stores anassociation to a function. Indirectly calling a function enables youto invoke the function regardless of where you call it from. Typicaluses of function handles include:

You can see if a variable, h, is a functionhandle using isa(h,'function_handle').

Creating Function Handles

To create a handle for a function, precede the function namewith an @ sign. For example, if you have a functioncalled myfunction, create a handle named f asfollows:

f = @myfunction;

You call a function using a handle the same way you call thefunction directly. For example, suppose that you have a function named computeSquare,defined as:

function y = computeSquare(x)y = x.^2;end

Create a handle and call the function to compute the squareof four.

f = @computeSquare;a = 4;b = f(a)

b = 16

If the function does not require any inputs, then you can callthe function with empty parentheses, such as

h = @ones;a = h()

a = 1

Without the parentheses, the assignment creates another functionhandle.

a = h

a = @ones

Function handles are variables that you can pass to other functions.For example, calculate the integral of x² onthe range [0,1].

q = integral(f,0,1);

Function handles store their absolute path, so when you havea valid handle, you can invoke the function from any location. Youdo not have to specify the path to the function when creating thehandle, only the function name.

Keep the following in mind when creating handles to functions:

Anonymous Functions

You can create handles to anonymous functions. An anonymousfunction is a one-line expression-based MATLAB function thatdoes not require a program file. Construct a handle to an anonymousfunction by defining the body of the function, anonymous_function,and a comma-separated list of input arguments to the anonymous function, arglist.The syntax is:

h = @(arglist)anonymous_function

For example, create a handle, sqr, to ananonymous function that computes the square of a number, and callthe anonymous function using its handle.

sqr = @(n) n.^2;x = sqr(3)

x = 9

For more information, see Anonymous Functions.

Arrays of Function Handles

You can create an array of function handles by collecting theminto a cell or structure array. For example, use a cell array:

C = {@sin, @cos, @tan};C{2}(pi)

ans = -1

Or use a structure array:

S.a = @sin; S.b = @cos; S.c = @tan;S.a(pi/2)

ans = 1

Saving and Loading Function Handles

You can save and load function handles in MATLAB, as you would any other variable. In other words, use the save and load functions. If you save a function handle, MATLAB saves the absolute path information. You can invoke the function from any location that MATLAB is able to reach, as long as the file for the function still exists at this location. An invalid handle occurs if the file location or file name has changed since you created the handle. If a handle is invalid, MATLAB might display a warning when you load the file. When you invoke an invalid handle, MATLAB issues an error.