nls error in formula

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


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