varlog.lam: Calculates the variance of the log rate of change between 2... In SightabilityModel: Wildlife Sightability Modeling

 varlog.lam R Documentation

Calculates the variance of the log rate of change between 2 population estimates that rely on the same sightability model.

Description

Calculates the variance of the log rate of change between 2 population estimates that rely on the same sightability model.

Usage

``````varlog.lam(sight1, sight2)
``````

Arguments

 `sight1` Sightability model object for the first population estimate (formed by calling Sight.Est function) `sight2` Sightability model object for the second population estimate (formed by calling Sight.Est function)

Details

This function uses the delta method to calculate an approximate variance for the log rate of change, log(tau^[t+1])-log(tau^[t]), while accounting for the positive covariance between the two estimates (as a result of using the same sightability model to correct for detection).

Value

 `loglambda` log rate of change = log(tau^[t+1]/tau^[t]) `varloglamda` approximate variance of loglambda

Author(s)

John Fieberg

`vardiff`

Examples

``````
# Example using moose survey data
data(obs.m) # observational moose survey data
data(exp.m) # experimental moose survey data
data(sampinfo.m) # information on sampling rates

# Estimate population size in 2006 and 2007
sampinfo <- sampinfo.m[sampinfo.m\$year==2007, ]
tau.2007 <- Sight.Est(observed ~ voc, odat = obs.m[obs.m\$year==2007, ],
sdat = exp.m, sampinfo.m[sampinfo.m\$year == 2007, ],
method = "Wong", logCI = TRUE, alpha = 0.05, Vm.boot = FALSE)
tau.2006 <- Sight.Est(observed ~ voc, odat = obs.m[obs.m\$year==2006, ],
sdat = exp.m, sampinfo.m[sampinfo.m\$year == 2006, ],
method = "Wong", logCI = TRUE, alpha = 0.05, Vm.boot = FALSE)

# Log rate of change
varlog.lam(tau.2006, tau.2007)

``````

SightabilityModel documentation built on Aug. 20, 2023, 1:08 a.m.