MATLAB Mathematics - SERC - Index of

4 Function Functions
Parameterizing Functions Called by Function Functions
At times, you might want use a function function that calls a function with
several parameters. For example, if you want to use fzero to find zeros of the
cubic polynomial x 3 + bx + c for different values of the coefficients b and c,
you would like the function that computes the polynomial to accept the
additional parameters b and c. When you invoke fzero, you must also provide
values for these additional parameters to the polynomial function. This section
describes two ways to do this:
• “Providing Parameter Values Using Nested Functions” on page 4-30
• “Providing Parameter Values to Anonymous Functions” on page 4-31
Providing Parameter Values Using Nested Functions
One way to provide parameters to the polynomial is to write a single M-file that
• Accepts the additional parameters as inputs
• Invokes the function function
• Contains the function called by the function function as a nested function
The following example illustrates how to find a zero of the cubic polynomial
x 3 + bx + c, for different values of the coefficients b and c, using this method.
To do so, write an M-file with the following code.
function y = findzero(b, c, x0)
options = optimset('Display', 'off'); % Turn off Display
y = fzero(@poly, x0, options);
function y = poly(x) % Compute the polynomial.
y = x^3 + b*x + c;
end
end
The main function, findzero, does two things:
• Invokes the function fzero to find a zero of the polynomial
• Computes the polynomial in a nested function, poly, which is called by fzero
4-30