flexhaz 0.5.2

• Prototype constructors (dfr_exponential(), dfr_weibull(), dfr_gompertz(), dfr_loglogistic()) now prepend a family-specific S3 subclass (e.g. "dfr_exponential") to the class chain. This enables downstream packages to dispatch on component type via inherits() rather than maintaining parallel lookup tables. Existing inherits(x, "dfr_dist") checks are unaffected (additive change).

flexhaz 0.5.1

• Initial CRAN release.
• Added JOSS paper (paper.md, paper.bib).
• Added community guidelines (CONTRIBUTING.md, CODE_OF_CONDUCT.md).
• Added Zenodo archive (DOI: 10.5281/zenodo.18757479).

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