R help - Sep 2009 - fitting logistic model with constant harvesting

Hi

I am fitting simulated data to a logistic model usin SSlogis as follow:

nls(
    cove ~ SSlogis(year, Asym, xmid, scal),
    data = dat,
    trace = TRUE,
    model = TRUE,
    ...
   )

This works niocely, but now I have a situation where I have constant
harvesting, i.e.


where p is the population size, N the carrying capacity, k the growth rate
and a the constant harvest.

My question is, how can I fit this logistic growth with constant harvesting
to my data?

Thanks,

Raine

-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

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