[R-sig-eco] calculate "dispersion index" (betadisper, vegan)

[Zoltan Botta-Dukat]

Hi Natalie,

Be careful with convex hull volume, because it is zero if points lie on 
a line (an near to zero, if the configuration is close to this), 
independently from the amount of distances.

Zoltan

2015.07.29. 19:26 keltezéssel, Natalie írta:
> hi all
>
> I would like to  calculate a dispersion index or similar from the 
> results of the vegan function betadisper.
> i would like to know if there is a possibility to e.g. calculate the 
> volume of the community dispersion(area of the hull in the PCoA) from 
> the betadisper results.
> common is to show the distance to the centroid.but I have the 
> impression the dispersion within communities are not that 
> clear,especially if you have similar variance.
> The program primer v5 calculates a disperion index based on  the 
> similarity percentage.
> similarity percentage is not an option since it is mainly based on 
> most counted species.
>
> ideas and help are very much appreciated
> cheers natalie
>
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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