Hello,

A parametric model (e.g. Clench) would allow both intrapolation and
extrapolation. There are some caveats of course: (1) these models arose in
the temporal accumulation sense, spatial accumulation is usually calculated
for randomized data, which is an assumption that individuals in the
sampling population are sufficiently mixed; (2) extrapolation from few
individuals won't be highly accurate; (3) this won't solve the N=0
situation, not even N=1.

Peter

--
Péter Sólymos, Dept Biol Sci, Univ Alberta, T6G 2E9, Canada AB
solymos@ualberta.ca, Ph 780.492.8534, http://psolymos.github.com
Alberta Biodiversity Monitoring Institute, http://www.abmi.ca
Boreal Avian Modelling Project, http://www.borealbirds.ca


On Fri, Oct 25, 2013 at 1:10 AM, Vít Syrovátka <syrovat@sci.muni.cz> wrote:

> Hi,
>
> vegan::rrarefy() is the right way to do this.
>
> However, I can't imagine, how to take 50 random individuals from a sample
> with less then 50 individuals.
> One doesn't know, what species would be collected in case of a larger
> sampling effort, R doesn't know either.
> I would suggest doing this only for samples with more individuals, or
> taking a smaller number of individuals.
>
> Hope that helps,
> Vit
>
> Dne 2013-10-24 21:08, Paris napsal:
>
>> By the way, I think I could use (if Zoop tha name of the dataset)
>> rrarefy(Zoop, sample=50).
>> However, in this case it will not allow me since there are samples with
>> zero
>> individuals.
>> Even if I delete those, there will be some with less than 50 indiv. But I
>> would prefer to standardise effort for 50 individuals. This function, or
>> at
>> least in this form, does not allow that.
>>
>>
>>
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