[R] nls error in formula

[Douglas Bates]

Anaid Diaz wrote:
> Hi,
> I'm a new R user, with a lot of questions. At the
> moment I'm stoped on an error traying to fit a model:
> 
> 
>>x <- sandeel ## numeric data (2500-60000)
>>y <- Noss   ## numeric data  (0-1.2)
>>A <- 0.8
>>B <- 0.6
>>C <- 1/40000
>>nls( y ~ A-B*exp(-C*x))
> 
> Error in match.call(definition, call, expand.dots) : 
>         .Primitive... is not a function
> 
> I'm not sure if the error is due to the formula sytax
> or something else.
> I'll appreciate any help
> 
> Sylvia

Use

nls(y ~ A -B*exp(-C*x), start = c(A = 0.8, B = 0.6, C = 1/40000))

instead or, preferably,

nls(y ~ SSasymp(x, Asym, R0, lrc))

and read

?SSasymp

for an interpretation of the estimated parameters.