Computes the Chao species estimator for abundance or presence-absence data
a vector, matrix or data frame with species by samples
a logical argument if the species are the rows or columns
chao1 will return an estimate of species richness based on a vector or matrix of abundance data, while
chao2 will return an estimate of species richness based on incidence data. Note that
chao1 estimator is for abundance data only. The
chao2 estimator can be given abundance data and it will automagically convert it to incidence data, but due to the nature of the estimator, the data must contain more than one sample (ie the data must be arranged in a minimum 2 by 2 matrix).
returns a value for the Chao Species Estimator for a the given data.
While the function will still return a value, if all the species abundances are equal to 1 in the input to
chao1, a warning will be raised, and the value returned will be equal to the number of species observed.
Chao, A. 1984. Non-parametric estimation of the number of classes in a population. Scandinavian Journal of Statistics 11: 265-270.
Chao, A. 1987. Estimating the Population Size for Capture-Recapture Data with Unequal Catchability. Biometrics 43: 783-791.
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Loading required package: sp Loading required package: maps Loading required package: shapefiles Loading required package: foreign Attaching package: 'shapefiles' The following objects are masked from 'package:foreign': read.dbf, write.dbf  11.5  4  6  6 Warning message: In chao1(a) : This data appears to be presence/absence based, but this estimator is for abundance data only  6
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