two.samp.cir: Computes analytical abundance estimates for two-sample...

In dill/wisp: Wildlife Simulation Package (wisp)

Description

Performs sex-specific harvest of animals from a simulated population, and produces analytical estimates of abundance and standard error for two-occasion change-in-ratio estimator.

Usage

two.samp.cir(rm.pop, frac.prehunt, frac.posthunt, frac.harv.male, frac.harv.fem)

Arguments

rm.pop	Population object being harvested and sampled (likely created by make.twosex.pop)
frac.prehunt	Proportion of the population sampled prior to the harvest
frac.posthunt	Proportion of the population sampled after to the harvest
frac.harv.male	Proportion of males in the population removed during harvest
frac.harv.fem	Proportion of females in the population removed during harvest

Details

This function augments the WiSP package by performing type-specific (think about type as equivalent to gender) harvest (or removal). The sampling process of a change-in-ratio study is to a) sample the population prior to the harvest to estimate sex ratio, b) harvest population in a sex specific manner, and c) sample population after harvest to again estimate sex ratio.

Value

point.cir	Estimated point estimate of abundance
se.cir	Standard error of abundance estimate
coef.var	Coefficient of variation of estimate (not percentage)

Warning

It is not impossible for the point estimate of abundance to be negative; particularly when the difference in harvest between males and females is small. This is a nonsensical result, and hence, the estimate is not considered admissable. In this situation, all values returned by this function are set equal to NA.

Note

Specifically, eqn. 5.15 of Borchers et al. (2002) is used for the point estimate, and 5.17 for the variance estimate. This function constitutes a building block of sim.cir.2 and its relative sim.cir.2.summary, in that repeated calls to two.samp.cir are made by these other functions to generate replicate realizations of an experiment.

Author(s)

Eric Rexstad, RUWPA [e-mail]

References

Borchers, Buckland, and Zucchini (2002), Estimating animal abundance: closed populations. Chapter 5 http://www.ruwpa.st-and.ac.uk/estimating.abundance

See Also

two.samp.cir, sim.cir.2, make.twosex.pop

Examples

library(wisp)
example.popn <- make.twosex.pop(abund=200, prop.male=0.4)
single.example.result <- two.samp.cir(rm.pop=example.popn, frac.prehunt=0.2, frac.posthunt=0.4,
                         frac.harv.male=0.6, frac.harv.fem=0.02)
single.example.result

dill/wisp documentation built on May 15, 2019, 8:31 a.m.