Gradient of the multiphase log-likelihood — .hzr_gradient

Computes the score vector \(d\ell / d\theta\) using analytic chain-rule formulas for log_mu and beta parameters, and central-difference derivatives (via .hzr_phase_derivatives()) for shape parameters (log_t_half, nu, m).

Usage

.hzr_gradient_multiphase(
  theta,
  time,
  status,
  time_lower = NULL,
  time_upper = NULL,
  x = NULL,
  weights = NULL,
  phases,
  covariate_counts,
  x_list,
  ...
)

Arguments

theta: Full parameter vector (internal scale).
time: Numeric vector of follow-up times (n).
status: Numeric event indicator: 1 = event, 0 = right-censored, -1 = left-censored, 2 = interval-censored.
time_lower: Optional lower bounds for interval censoring.
time_upper: Optional upper bounds for left/interval censoring.
x: Design matrix (unused directly; kept for interface compatibility).
phases: Named list of validated hzr_phase objects.
covariate_counts: Named integer vector of per-phase covariate counts.
x_list: Named list of per-phase design matrices.
...: Ignored.

Value

Numeric vector of length length(theta) – the gradient. Returns a zero vector if any component is non-finite (guards optimizer).