rstrat {recapr}

Random Draws from the Stratified Estimator

Description

Returns a vector of random draws from the stratified estimator in a mark-recapture experiment, given values of the true abundance and the sample size in both events. The function first simulates a vector of recaptures (m2) for each stratum, and then uses these to compute a vector of draws from the estimator.

It may prove useful to investigate the behavior of the stratified estimator under relevant scenarios.

If capture probabilities (p1 and/or p2) are specified instead of sample size(s), the sample size(s) will first be drawn from a binomial distribution, then the number of recaptures. If both sample size and capture probability are specified for a given sampling event, only the sample size will be used.

Usage

rstrat(
  length,
  N,
  n1 = NULL,
  n2 = NULL,
  p1 = NULL,
  p2 = NULL,
  estimator = "Chapman"
)

Arguments

length

The length of the random vector to return.

N

A vector of values of the true abundance for each stratum.

n1

A vector of the number of individuals captured and marked in the first sample, for each stratum.

n2

A vector of the number of individuals captured in the second sample, for each stratum.

p1

Alternately, a vector of probabilities of capture for the first event, for each stratum.

p2

Alternately, a vector of probabilities of capture for the second event, for each stratum.

estimator

The type of estimator to use. Allowed values are "Chapman", "Petersen", and "Bailey". Default to "Chapman".

Value

A vector of random draws from the stratified estimator

Author(s)

Matt Tyers

See Also

strattest, Nstrat, vstrat, cistrat,NChapman, NPetersen, NBailey

Examples

draws <- rstrat(length=100000, N=c(5000,10000), n1=c(500,200), n2=c(500,200))
plotdiscdensity(draws)  #plots the density of a vector of discrete values
mean(draws)