R: ZTP estimator

ztp.rSAC {preseqR} | R Documentation

## ZTP estimator

### Description

`ztp.rSAC` predicts the expected number of species represented at least r times in a random sample, based on the initial sample.

### Usage

    ztp.rSAC(n, r=1)

### Arguments

`n` | A two-column matrix. The first column is the frequency j = 1,2,…; and the second column is N_j, the number of species with each species represented exactly j times in the initial sample. The first column must be sorted in an ascending order.
`r` | A positive integer. Default is 1.

### Details

The statistical assumption is that for each species the number of individuals in a sample follows a Poisson distribution. The Poisson rate `lambda` is the same among all species. So the random variable `X`, which is the number of species represented x (x > 0) times, follows a zero-truncated Poisson distribution. The unknown parameters are estimated by Cohen (1960). Based on the estimated distribution, we calculate the expected number of species in a random sample.

### Value

The estimator for the r-SAC. The input of the estimator is a vector of sampling efforts t, i.e., the relative sample sizes comparing with the initial sample. For example, t = 2 means a random sample that is twice the size of the initial sample.

### Author(s)

Chao Deng

### References

Cohen, A. Clifford. "Estimating the parameter in a conditional Poisson distribution." Biometrics 16, no. 2 (1960): 203-211.

### Examples

    ## load library
    library(preseqR)

    ## import data
    data(FisherButterfly)

    ## construct the estimator for SAC
    ztp1 <- ztp.rSAC(FisherButterfly, r=1)
    ## The number of species represented at least once in a sample,
    ## when the sample size is 10 or 20 times of the initial sample
    ztp1(c(10, 20))

    ## construct the estimator for r-SAC
    ztp2 <- ztp.rSAC(FisherButterfly, r=2)
    ## The number of species represented at least once in a sample,
    ## when the sample size is 10 or 20 times of the initial sample
    ztp2(c(50, 100))

[Package preseqR version 4.0.0 Index]