R help - Sep 2010 - Finding Zeros of a Function

Dear All,
I need to find the (possible multiple) zeros of a function f within an 
interval. I gave uniroot a try, but it just returns one zero and I need 
to provide it with an interval [a,b] such that f(a)f(b)<0.
Is there any function to find the multiple zeros of f in (a,b) without 
constraints on the sign of f(a) and f(b)?
Many thanks

Lorenzo

Dear Lorenzo,

You could try the BB package:

# function we need the roots for

fn1 <- function(x, a) - x^2 + x + a


 # plot

curve(fn1(x, a = 5), -4, 4)

abline(h=0, col = 2)


 # searching the roots in (-4, 4)

# install.packages('BB')

require(BB)

BBsolve(par = c(-1, 1), fn = fn1, a = 5)

values <- BBsolve(par = c(-1, 1), fn = fn1, a = 5)$par

values


 # adding the roots to the plot

points(values, c(0, 0), pch = 8, cex = 1.1, col = 4)

HTH,
Jorge


On Sat, Sep 25, 2010 at 8:24 PM, Lorenzo Isella <> wrote:
> Dear All,
> I need to find the (possible multiple) zeros of a function f within an
> interval. I gave uniroot a try, but it just returns one zero and I need to
> provide it with an interval [a,b] such that f(a)f(b)<0.
> Is there any function to find the multiple zeros of f in (a,b) without
> constraints on the sign of f(a) and f(b)?
> Many thanks
>
> Lorenzo
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

You may also try package nleqslv, which uses  Newton or Broyden to solve  a
system of nonlinear equations. It is an alternative to BB.
Without further information from your side, no additional information can be
provided.

/Berend
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