Description Usage Arguments Details Value Author(s) References See Also
View source: R/Wong.est.Ratio.R
Estimates population ratio, with variance estimated using Wong's (1996) estimator. This function will usually be called by Sight.Est,Ratio() function (but see details).
1 2 3 4 5 6 7 8 9 10 11 12 13  Wong.est.Ratio(
numerator,
denominator,
srates,
nh,
Nh,
stratum,
subunit,
covars,
beta,
varbeta,
smat = NULL
)

numerator, denominator 
Number of animals in numerator and denominator of each independently sighted group 
srates 
Vector of plotlevel sampling probabilities (same dimension as

nh 
Number of sample plots in each stratum 
Nh 
Number of population plots in each stratum 
stratum 
Stratum identifiers (associated with the independently observed animal groups) 
subunit 
Plot ID (associated with the independently observed animal groups) 
covars 
Matrix of sightability covariates (associated with the independently observed animal groups) 
beta 
Logistic regression parameter estimates (from fitted sightability model) 
varbeta 
Estimated variancecovariance matrix for the logistic regression parameter estimates (from fitted sightability model) 
smat 
Estimated variancecovariance matrix for the inflation factors (1/probability of detection). This is an n.animal x n.animal matrix, and is usually calculated within the Wong.est function. Nonnull values can be passed to the function (e.g., if a bootstrap is used to estimate uncertainty due to the estimated detection parameters). 
This function is called by Sight.Est.Ratio, but may also be called directly by the user (e.g., in cases where the original sightability [test trial] data are not available, but the parameters and var/cov matrix from the logistic regression model is available in the literature).
ratio.hat 
Sightability estimate of ratio, ratio^ 
Vartot 
Estimated variance of ratio^ 
VarSamp, VarSight,
VarMod 
Estimated variance component due to sampling, sightability, model are set to NA 
Carl James Schwarz cschwarz.stat.sfu.ca@gmail.com
Rice CG, Jenkins KJ, Chang WY (2009). Sightability Model for Mountain Goats." The Journal of Wildlife Management, 73(3), 468 478.
Steinhorst, R. K., and M.D. Samuel. (1989). Sightability adjustment methods for aerial surveys of wildlife populations. Biometrics 45:415425.
Wong, C. (1996). Population size estimation using the modified HorvitzThompson estimator with estimated sighting probabilities. Dissertation, Colorado State University, Fort Collins, USA.
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