simpson {benthos} | R Documentation |
The probability that two inidividuals selected at random (with replacement, Hurlbert, 1971, p.579) from a sample will belong to the same species. For an infinite sample Simpson's Index is given by (Peet, 1974):
λ = ∑_{i=1}^S p_i^2
For a finite sample by:
L = ∑_{i=1}^S \frac{n_i (n_i-1)}{N (N-1)}
where p[i] the proportion of the individuals in species i,
n[i] the number of individuals in species
i (relative abundance
), and N the total number
of individuals (total_abundance
). The finite sample case
has been implemented in function simpson
(and simpson_
).
simpson(.data = NULL, taxon, count) simpson_(.data = NULL, taxon, count)
.data |
data in a |
taxon |
name of column in |
count |
name of column in |
The probability that two inidividuals selected at random from a sample will belong to the same species.
simpson_
: version suitable for calling from a function
(see package lazyeval).
Peet, R. K. 1974, The Measurement of Species Diversity. Annual Review of Ecology and Systematics 5:285-307.
simpson( taxon = c("Euspira pulchella", "Nephtys cirrosa"), count = c(6, 12) )