Negative log-likelihood for Tobit half-life regression

Helper function used by fit_half_life_tobit() via stats::optim(). For observations above the LLOQ, the normal density contributes to the likelihood. For censored (BLQ) observations, the normal CDF up to the LLOQ contributes.

Usage

fit_half_life_tobit_LL(par, log_conc, time, mask_blq, log_lloq)

Arguments

par

A 3-element numeric vector: c(log_c0, lambda_z, log_resid_error)

log_conc

Natural log of observed concentration (may be -Inf for BLQ; those values are not used when mask_blq is TRUE)

time

Numeric time vector

mask_blq

Logical vector; TRUE where the observation is below the LLOQ

log_lloq

Natural log of the lower limit of quantification

Value

The negative sum of the log-likelihood (a scalar)

See also

fit_half_life_tobit()