# [R] nls question

ben@zoo.ufl.edu ben at zoo.ufl.edu
Fri Apr 27 15:50:39 CEST 2001

```  I think you need to make your parameter/parameter vector the *first*
argument to your function.  That way the "..." gets interpreted
correctly.  e.g.:

fn2<-function(p,x,y)
{
yhat<-p*x+(1-p)
sum((y-yhat)^2)
}

out <- nlm(fn2,p=1.5,x=x, y=y,hessian=TRUE)

On Fri, 27 Apr 2001, Bill Simpson wrote:

> I have a question about passing arguments to the function f that nlm
> minimizes.
>
> I have no problems if I do this:
> x<-seq(0,1,.1)
> y<-1.1*x + (1-1.1) + rnorm(length(x),0,.1)
> fn<-function(p)
> 	{
> 	yhat<-p*x+(1-p)
> 	sum((y-yhat)^2)
> 	}
> out<-nlm(fn,p=1.5,hessian=TRUE)
>
> But I would like to define
> fn<-function(x,y,p)
>         {
>         yhat<-p*x+(1-p)
>         sum((y-yhat)^2)
>         }
> so that I can pass the x and y variables along, doing something like
> out<-nlm(fn,x=this, y=that,p=1.5,hessian=TRUE)
> This version doesn't work of course. I have looked at the examples and
> can't figure out how to do what I want. Is it possible?
>
> Thanks very much for any help.
>
> (BTW I know nls() can be used for nonlinear least squares fitting. It
> choked on this problem.)
>
> Bill Simpson
>
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--
318 Carr Hall                                bolker at zoo.ufl.edu
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