[R] Solve f(x) = 0

[Spencer Graves]

	  Have you plotted f(x)?  Plot(s) might help reveal why "the solution 
is very unstable."  If f is a function of a univariate x, this is 
trivial.  If f is a function of a bivariate x, use something like 
contour or persp.  If higher dimensions, I might use something like

	  fit <- optim(... hessian=TRUE)
	  eigen(fit$hessian)

	  hope this helps.
	  spencer graves

Martyn Plummer wrote:

> On Wed, 2005-06-08 at 17:08 +0200, Fredrik Thuring wrote:
> 
>>Hi!
>>
>>Im need a function that solves the equation f(x) = 0 (i.e. the root of
>>the function) when f is a nonlinear function. Is there any? Ive tried nlm
>>and optim on the square of the function but the solution is very unstable.
> 
> 
> Your colleague Martin Englund asked the same question.  If x is scalar,
> you can use uniroot(). If it's a polynomial then polyroot() finds all
> the zeros. I hope that helps.
> 
> Martyn
> 
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