Rygg's index of diversity is given by
$$SN = \frac{\ln(S)}{\ln(\ln(N))}$$
Usage
rygg(taxon, count, adjusted = FALSE)
Value
Rygg's index of diversity (numeric
vector of length 1)
Arguments
taxon
taxa names (character)
count
counts (numeric)
adjusted
(defaults to FALSE)
Details
The adjusted version of Rygg's index which gives more consistent values
for smaller S=2, N=2, N=3 and S=3, N=3 is
$$SN = \frac{\ln(S)}{\ln(\ln(N+1)+1)}$$
References
Rygg, B. (2006). Developing indices for quality-status
classification of marine soft-bottom fauna in Norway.
Norwegian Institute for Water Research, Oslo, Norway.
NIVA Report SNO 5208-2006.