Re: [R] Solve f(x) = 0

From: Spencer Graves <spencer.graves_at_pdf.com>
Date: Thu 09 Jun 2005 - 02:20:31 EST

          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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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jun 09 02:27:29 2005

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