[R-sig-eco] slope for rarefaction curve

[Zoltan Botta-Dukat]

Dear Simone,

Function "rarefy" uses the function developed by Hurlbert, thus if you 
need slope in a certain point (as your graph suggests) you can calculate 
the derivative of this function. It is not an easy job, because 
factorials should be derived. See cues here how it can be done:

http://math.stackexchange.com/questions/300526/derivative-of-a-factorial

If you need mean slope in an interval, simply calculate the difference 
in the calculated values for the beginning and end of the interval, and 
divide the difference by the length of the interval.

Zoltan

2015.05.10. 23:57 keltezéssel, Simone Ruzza írta:
> Dear all,
>
> apologies for the total beginner's question. I was wondering if anyone
> can give some advice on how to calculate the slope for the last 10% of
> the records of a rarefaction curve computed with rarefy from vegan.
> Here is a graphic representation of what I would like to do:
>
> https://dl.dropboxusercontent.com/u/33966347/figure.JPG
>
> I have seen that this has been done in a recent paper and I was
> wondering if anyone may have any code snippet to do that. Sorry, maybe
> this is something really obvious but I have not quite understood how
> to do it.
>
> thanks!
>
> Simone
>
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-- 
Botta-Dukát Zoltán
--------------------------------
Ökológiai és Botanikai Intézet
Magyar Tudományos Akadémia
Ökológiai Kutatóközpont
--------------------------------
2163. Vácrátót, Alkotmány u. 2-4.
tel: +36 28 360122/157
fax: +36 28 360110
botta-dukat.zoltan at okologia.mta.hu
www.okologia.mta.hu


Zoltán BOTTA-Dukát
--------------------------------
Institute of Ecology and Botany
Hungarian Academy of Sciences
Centre for Ecological Research
--------------------------------
H-2163 Vácrátót, Alkomány u. 2-4.
HUNGARY
Phone: +36 28 360122/157
Fax..: +36 28 360110
botta-dukat.zoltan at okologia.mta.hu
www.okologia.mta.hu