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Pass Function to Another Function

You can use function handles as input arguments to other functions, which are called function functions. These functions evaluate mathematical expressions over a range of values. Typical function functions include integral, quad2d, fzero, and fminbnd.

For example, to find the integral of the natural log from 0 through 5, pass a handle to the log function to integral.

a = 0;
b = 5;
q1 = integral(@log,a,b)
q1 = 3.0472

Similarly, to find the integral of the sin function and the exp function, pass handles to those functions to integral.

q2 = integral(@sin,a,b)
q2 = 0.7163
q3 = integral(@exp,a,b)
q3 = 147.4132

Also, you can pass a handle to an anonymous function to function functions. An anonymous function is a one-line expression-based MATLAB® function that does not require a program file. For example, evaluate the integral of x/(ex-1) on the range [0,Inf]:

fun = @(x)x./(exp(x)-1);
q4 = integral(fun,0,Inf)
q4 = 1.6449

Functions that take a function as an input (called function functions) expect that the function associated with the function handle has a certain number of input variables. For example, if you call integral or fzero, the function associated with the function handle must have exactly one input variable. If you call integral3, the function associated with the function handle must have three input variables. For information on calling function functions with more variables, see Parameterizing Functions.

You can write functions that accept function handles the same way as writing functions to accept other types of inputs. Write a function that doubles the output of the input function handle for a given input.

function x = doubleFunction(funHandle,funInput)
    x = 2*funHandle(funInput);

Test this function by providing a function handle as the input.

x = doubleFunction(fun,4)
x = 0.1493

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