Providing Parameter Values to Anonymous Functions :: Function Functions (Mathematics)

Mathematics

Providing Parameter Values to Anonymous Functions

Suppose you have already written a standalone M-file for the function poly containing the following code, which computes the polynomial for any coefficients b and c,

function y = poly(x, b, c) % Compute the polynomial.
y = x^3 + b*x + c;

You then want to find a zero for the coefficient values b = 2 and c = 3.5. You cannot simply apply fzero to poly, which has three input arguments, because fzero only accepts functions with a single input argument. As an alternative to rewriting poly as a nested function, as described in Providing Parameter Values Using Nested Functions, you can pass poly to fzero as a function handle to an anonymous function that has the form @(x) poly(x, b, c). The function handle has just one input argument x, so fzero accepts it.

b = 2;
c = 3.5;
x = fzero(@(x) poly(x, b, c), 0)

This returns the zero

```
x =

   -1.0945
```

Anonymous Functions explains how to create anonymous functions.

If you later decide to find a zero for different values of b and c, you must redefine the anonymous function using the new values. For example,

b = 4;
c = -1;
fzero(@(x) poly(x, b, c), 0)

ans =

    0.2463

For more complicated objective functions, it is usually preferable to write the function as a nested function, as described in Providing Parameter Values Using Nested Functions.

Providing Parameter Values Using Nested Functions Differential Equations