flexhaz 0.5.0

Changes

• Added helper distribution constructors: dfr_exponential(), dfr_weibull(), dfr_gompertz(), dfr_loglogistic() with analytical hazard, cumulative hazard, score, and Hessian functions where available.
• Added diagnostic methods: residuals() (Cox-Snell and Martingale), plot() (survival, hazard, cumulative hazard), qqplot_residuals().
• Added density() method (alias for pdf).
• Added assumptions() method for listing model assumptions.
• Added kaplan_meier() internal utility for empirical survival estimation.
• Added support for left-censored observations (delta = -1).
• Improved numerical stability in log-likelihood computation.
• Removed femtograd dependency — users supply their own derivative functions via score_fn and hess_fn, or the package falls back to numDeriv.

flexhaz 0.1.0

Initial release.

Features

• dfr_dist() constructor for creating distributions from hazard functions
• Complete distribution interface: hazard(), cum_haz(), surv(), cdf(), pdf(), inv_cdf(), sampler()
• Likelihood model interface: loglik(), score(), hess_loglik(), fit()
• Support for right-censored survival data
• Numerical integration for cumulative hazard
• Inverse CDF sampling

Examples

Supports modeling complex hazard patterns:

• Exponential (constant hazard)
• Weibull (monotonic hazard)
• Bathtub curves (infant mortality + useful life + wear-out)
• Proportional hazards with covariates