Time-to-detection occupancy family

Occupancy where a survey records the TIME to first detection rather than a 0/1 outcome (Garrard et al. 2008; unmarked occuTTD). At an occupied site the time-to-detection is exponential with rate lambda (constant hazard); a survey of length surveyLength that reaches its end without a detection is censored. An unoccupied site never detects. The state formula models logit psi (occupancy); detection models log lambda (the site-level detection rate). The latent occupancy state integrates out in closed form (two states), so the fit maximises the exact marginal with an observed-information vcov.

Usage

occu_ttd(surveyLength = 1)

Arguments

surveyLength

Survey length Tmax (the censoring time): a scalar, a length-N vector, or an N x J matrix. Default 1.

Value

A tobs_family object for tobs().

Details

y is an N x J matrix of detection times: a value in (0, surveyLength) is a detection; a value >= surveyLength is a non-detection (censored); NA is a survey not conducted.

Examples

# \donttest{
sim <- simulate_occu_ttd(N = 200, J = 4, Tmax = 3, seed = 1)
fit <- tobs(~ psi_cov1, data = sim$data, family = occu_ttd(surveyLength = 3),
            detection = ~ rate_cov1, y = sim$y, control = list(verbose = FALSE))
coef(fit)
# }