Message-ID: <4263BF5C.1060907@stat.wisc.edu>
Date: 2005-04-18T14:08:28Z
From: Douglas Bates
Subject: nls error in formula
In-Reply-To: <20050418135442.88474.qmail@web51909.mail.yahoo.com>
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.