[R-sig-Geo] slope for rarefaction curve

[Simone Ruzza]

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