
going through the uniroot, it seems like the crux is in .fGBSVolatility where the function is defined, unless I am missing the point. apologies if I am .... perhaps the more relevant question would have been me requesting reference to .fGBSVolatility....
 > From: josh.m.ulrich@gmail.com
> Date: Tue, 1 Nov 2011 19:48:11 -0500
> Subject: Re: [R-SIG-Finance] GBSVolatility in fOptions
> To: fin_engr@hotmail.com
> CC: r-sig-finance@r-project.org
> 
> You have the source code.  Take a look:
> 
> GBSVolatility = function(price, TypeFlag = c("c", "p"), S, X, Time, r, b,
> tol = .Machine$double.eps, maxiter = 10000)
> {
>     TypeFlag = TypeFlag[1]
>     volatility = uniroot(.fGBSVolatility, interval = c(-10,10), price = price,
>         TypeFlag = TypeFlag, S = S, X = X, Time = Time, r = r, b = b,
>         tol = tol, maxiter = maxiter)$root
>    volatility
> }
> 
> There you go.  Now you can read ?uniroot to see what it does.
> --
> Joshua Ulrich  |  FOSS Trading: www.fosstrading.com
> 
> 
> 
> On Tue, Nov 1, 2011 at 6:59 PM, financial engineer <fin_engr@hotmail.com> wrote:
> >
> > hi,
> > Can anyone shed some light on which root-finding algorithm the GBSVolatility function uses - is it the Newton method?
> > thanks,
> > BA
> >
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