Re: fzero tolerance issue ... and a related bug

[Martin Helm]

Am 18.10.2012 19:46, schrieb Joza:
> So related to all that above, how does one find the root of a function that
> is always positive, or zero, but never negative? For instance, an absolute
> value:  f(x) = abs(x - 2)
>
> This has root 2, but I can't give it an initial bracket [x1,x2] since
> f(x2)*f(x2) >= 0.
> Indeed, how could fzero even find an initial bracket?
>
> So how can one solve such a simple equation with fzero?
>
You simply do not solve such an equation with fzero since it does not
belong to the class of equations fzero is made for, instead use fsolve
fsolve( @(x) abs(x-9.1)^4.5, 8, optimset("TolFun", 1e-20))
ans =  9.0999