fzero

Syntax

x = fzero(@func,interval)

x = fzero(@func,interval,options)

[x,fval,info,output] = fzero(...)

Inputs

func

The function whose root is to be found.

interval

A two-element vector containing the root.

Type: double

Dimension: vector

options

A struct containing option settings.

See optimset for details.

Outputs

x

The location of the approximate root.

fval

The function value at the approximate root.

info

The convergence status flag.

info = 1

Function value converged to within tolX.

info = 0

Reached maximum number of iterations or function calls.

output

A struct containing iteration details. The members are as follows:

iterations

The number of iterations.

nfev

The number of function evaluations.

xiter

The function values of the interval end points at each iteration.

fvaliter

The interval end points at each iteration.

Examples

function y = func(x)
    y = (x-3)^4 - 16;
end

options = optimset('TolX', 1.0e-8);
interval = [1, 6];
[x,fval] = fzero(@func, interval, options)

x = 4.99999999
fval = -4.18902e-07

function y = func(x, offset)
    y = (x-3)^4 + offset;
end

handle = @(x) func(x, -8);
[x,fval] = fzero(handle, interval, options)

x = 1.31820717
fval = 3.55271e-15

Comments

fzero implements ACM Transactions on Mathematical Software algorithm 748, which does not require derivatives.

Options for convergence tolerance controls are specified with optimset.

To pass additional parameters to a function argument, use an anonymous function.