evenness {asbio} | R Documentation |
Calculates Pielou's measure of species evenness, i.e. J = H'/ln(S) where H' is Shannon Weiner diversity and S is the total number of species in a sample, across all samples in dataset.
evenness(x)
x |
A vector or matrix of species abundances (e.g. counts). The function assumes that species are in columns and sites are in rows. |
Many diveristy indices incoporate evenness (e.g. Simpson's diversity, Shannon- Weiner diversity). Diversity indices which concentrate totally on evenness are fraught with problems including dependence on species counts (McCune and Grace 2002). A particular problem with Pielou's index is that it is a ratio of a relatively stable index, H', and one that is strongly dependent on sample size, S.
Returns Pielou's J.
Ken Aho
McCune, B., and Grace, J.B. (2002) Analysis of ecological communities. MjM Software design. Gelenden Beach OR.
library(vegan) data(varespec) evenness(varespec)