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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