This menu can used to calculate measures of diversity and bootstrap
confidence intervals. A diversity index is a measure of species
diversity within a community that consists of co-occurring populations
of several (two or more) different
species. There are many different diversity indices that combine species
richness and evenness, the two elements of diversity, in different ways.
Amongst these indices are
the log-series alpha and log-Normal lambda which are estimated by fitting
an underlying species abundance model, and the Q statistic which is derived
from cumulative ranked frequencies. Other available indices include the
Margalef and Simpsons 1/D which emphasize the richness component of
diversity. The indices that highlight the evenness component of diversity
include Simpsons 1-D, McIntosh D and E, Shannon-Weiner H' and J', Brillouin
diversity and evenness index, Berger-Parker and Smith-Wilson evenness measure.
See the ECDIVERSITY procedure for
further details about the calculation of the indices. Confidence intervals for
the measures can be estimated by bootstrapping. For multiple samples,
the overall values of the diversity indices are calculated an option is available
to perform jackknifing to produce less bias estimates with a confidence interval.
Data format
Specifies to format of the data. Select Single variate
to supply the individuals in a single variate. Alternatively, select
Multiple variates, if the data are to be
supplied in multiple samples of individuals.
Individuals
A variate containing the numbers of individuals per species.
Species
A variate containing the number of species for the associated number of individuals
in the corresponding element of Individuals. This field
can be left empty if each of the values in Individuals
corresponds to one species.
Groups
A factor specifying the groups for the different samples.
Samples
For multiple samples this allows you to specify one or more variates containing the
individuals for different samples. Multiple selections can be transferred from the
Available data list by clicking the
button.
Indices
Controls the type of index that is to be calculated. You can select one of more
of the indices. See the ECDIVERSITY procedure for
further details about the calculation of each index.
Available Data
This lists data structures appropriate to the current input field. The contents will change as you move from one field to the
next. Double-click on a name to copy it to the current input field; alternatively, you can type the name directly into the input field.
Options
Additional options are available to produce confidence intervals for
the measures by bootstrapping. Also for multiple samples, an option is available
to perform jackknifing to produce less bias estimates with a confidence interval.
See Also