aniso: Spatially Explicit Capture-Recapture in Transformed Space

Description Usage Arguments Details Value References See Also Examples

Description

Fits SECR model using distances calculated in a space transformed by compression along a single axis. Both the orientation of the axis (ψ_A) and the compression ratio (ψ_R) are treated as parameters to be estimated. The general method was first applied by Murphy et al. (2016).

Usage

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anisotropic.fit(..., psiA = pi/4, psiR = 2)

predictAniso(fit, angle = c("degrees", "radians"))

Arguments

...

arguments passed to ]secr.fit

psiA

numeric initial value of phiA

psiR

numeric initial value of phiR

fit

fitted model from anisotropic.fit

angle

units for angle

Details

The compression ratio ψ_R takes values greater than or equal to 1.0. The corresponding coefficient on the link scale is log(ψ_R - 1).

The function predictAniso extracts estimates of the transformation parameters from a fitted model and back-transforms psiR.

The estimate of the spatial scale parameter sigma applies in the isotropic compressed space; it may be understood as an estimate along the minor axis of each ellipse.

Value

For anisotropic.fit, a fitted secr model.

For predictAniso, a dataframe of two rows (psiA, psiR).

References

Murphy, S. M., Cox, J. J., Augustine, B. C., Hast, J. T., Guthrie, J. M., Wright, J., McDermott, J., Maehr, S. C. and Plaxico, J. H. (2016) Characterizing recolonization by a reintroduced bear population using genetic spatial capture–recapture. Journal of Wildlife Management 80, 1390–1407.

See Also

secr.fit

Examples

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## view the function used internally for distances
secrBVN:::anisodistfn

## simulate data
tr <- make.grid(10, 10, spacing = 25, hollow = TRUE, detector = 'proximity')
pop <- simpopn.bvn(s2xy = (25*c(0.5,2))^2, theta = pi/4, core = tr, buffer = 200, 
                   D = 4, Ndist = 'fixed')
CH <- simcapt.bvn(tr, pop, type = 'BVN', lambda = 0.4, noccasions = 5)

## fit model
fit <- anisotropic.fit(CH, buffer = 200, detectfn = 'HHN', trace = FALSE)

## examine results
coef(fit)
predictAniso(fit)
predict(fit)

MurrayEfford/secrBVN documentation built on May 26, 2019, 4:38 p.m.