rygg {benthos}

Rygg's Index of Diversity

Description

Rygg's index of diversity is given by

SN = \frac{\ln(S)}{\ln(\ln(N))}

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)}

Usage

rygg(.data = NULL, taxon, count, adjusted = FALSE)

rygg_(.data = NULL, taxon, count, adjusted = FALSE)

Arguments

.data

data in a data.frame, tibble, data.table, database etc.

taxon

taxa names (character)

count

counts (numeric)

adjusted

(defaults to FALSE)

Value

Rygg's index of diversity (numeric vector of length 1)

Functions

• rygg_(): version suitable for calling from a function (see package lazyeval).

Note

Rygg's index is not defined for N=exp(1). For N \leq exp(1), rygg returns NA_real_.

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.

Examples

 rygg(
     taxon = c("Euspira pulchella", "Nephtys cirrosa"), 
     count = c(4, 6)
 )