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kofn 0.4.0

Breaking changes

The kofn() constructor now takes a component argument (a dfr_dist prototype from flexhaz) instead of a stringy family argument:

# Before (0.3.x):
kofn(k = 2, m = 3, family = "exponential")
kofn(k = 2, m = 3, family = "weibull")

# After (0.4.0):
kofn(k = 2, m = 3, component = dfr_exponential())
kofn(k = 2, m = 3, component = dfr_weibull())

Rationale: object-based component specification composes with the rest of the ecosystem (flexhaz, serieshaz, maskedhaz) and makes the supported-family table a property of class dispatch rather than a parallel lookup in match.arg. Adding future supported component families is now a one-line change.

The same rename applies to compare_fisher_info():

# Before:
compare_fisher_info(rates = c(1, 2), family = "exponential", ...)

# After:
compare_fisher_info(rates = c(1, 2), component = dfr_exponential(), ...)

Internal helpers parse_params(), kofn_dgp(), and kofn_components() take component rather than family. These were @keywords internal and not part of the public API, but downstream code that touched them via ::: will need the same rename.

New internal helpers

• n_par_kofn(m, component): expected parameter count for a homogeneous kofn system, replacing inline switch(family, ...) logic.
• kofn_subclass(component): maps a dfr_dist prototype to the corresponding kofn subclass (exp_kofn or wei_kofn).

Dependencies

• Added flexhaz (>= 0.5.2) to Imports. The dfr_dist prototype constructors provide family-specific S3 subclasses (dfr_exponential, dfr_weibull) that kofn_subclass() dispatches on.

Bug fixes

• compare_fisher_info(): corrected the Weibull complete-data (Scheme 2) Fisher information formula. The shape-shape entry had a spurious leading 1 (about 55 percent too large) and the shape-scale cross term was divided by alpha * beta instead of beta. Both errors vanish at shape 1 (the exponential boundary), which is why exponential results were unaffected. The analytic block now lives in an internal helper verified against numerically integrated expected information in the test suite. Scheme 0/1 results (numerical Hessians) were never affected; for Weibull components, Scheme 2 determinants and the efficiency ratios involving Scheme 2 change.
• Interval-censored rows in a data frame lacking the upper-bound column (t_upper by default) now fail with an informative error in all likelihood paths. Previously the exponential parallel fast path crashed with “missing value where TRUE/FALSE needed” and the general-k path silently returned -Inf.

kofn 0.3.1

Documentation

• Vignettes restructured around the post-refactor package scope. Deleted outdated vignettes (censoring-framework, kofn-systems, general-kofn, symmetry-breaking) that documented removed topology / general-system APIs; added:
  • getting-started: quick tour of the kofn model, fit, and observation schemes.
  • dist-structure-integration: how kofn delegates DGP and topology to dist.structure, convention conversion, migration notes for v0.2.0 users.
• Added _pkgdown.yml configuring navbar, article menus, and a reference index grouped by theme.
• Retained and verified: exponential-parallel, observation-schemes, weibull-em, periodic-inspection, ecosystem.

kofn 0.3.0

Major refactor: dist.structure adoption

kofn now delegates the data-generating process (DGP), topology, and system-level distribution generics to dist.structure. The package focuses exclusively on inference for k-out-of-n systems: log-likelihood, score, Hessian, fit, observation schemes (right/left/interval/periodic), masked cause-of-failure, periodic-inspection (Scheme 1), and Fisher information comparison.

Removed

• coherent_system(), parallel_system(), series_system(), kofn_system(), bridge_system(), consecutive_k_system(): use the corresponding constructors in dist.structure (coherent_dist, parallel_dist, series_dist, kofn_dist, bridge_dist, consecutive_k_dist).
• system_signature(), system_lifetime(), system_censoring(), critical_states(), min_paths(), min_cuts(), phi(), min_cuts_from_paths(), minimize_sets(): use dist.structure equivalents (registered on every dist_structure subclass).
• loglik_system(), fit_system(), rdata_system(): replaced by the loglik/fit/rdata S3 methods on kofn model objects (for k-of-n) plus the dist generics on dist.structure::exp_kofn, wei_kofn, coherent_dist (for general topologies).
• f_sys_general(), S_sys_general(): use algebraic.dist::density() and surv() on a dist.structure object.
• make_dists(), exp_dist(), weibull_dist() (the lightweight $pdf/$cdf/$surv list interface): replaced by algebraic.dist::exponential() and weibull_dist() plus the algebraic.dist generics.

Changed

• kofn() constructor no longer accepts a system = ... argument. kofn is now exclusively for k-of-n estimation. Users with non-k-of-n topologies should use dist.structure::coherent_dist() directly.
• loglik.exp_kofn and loglik.wei_kofn general-k path now delegates per-observation contributions to dist.structure::exp_kofn(k_dist, par) and wei_kofn(k_dist, shapes, scales) via the algebraic.dist density, surv, and cdf generics. Parallel-fast-path (k=m) IE expansion is preserved as the closed-form path.
• loglik_scheme1 system density now uses density(dist.structure::exp_kofn(...)) / wei_kofn(...) instead of the local f_sys_general engine.
• rdata.exp_kofn, rdata.wei_kofn, rdata_masked, rdata_scheme1 use a kofn-internal specialized kofn_censoring(k, times) helper (the k-th order statistic) instead of the general system_censoring algorithm.
• assumptions.exp_kofn and assumptions.wei_kofn no longer mention “general coherent system” since kofn is k-of-n only.

Internal

• New file R/internal_topology.R with private helpers kofn_censoring(), kofn_dgp(), kofn_components(). Uses the k_dist = m - k_kofn + 1 conversion between kofn’s :F convention (k_kofn = number of failures triggering system failure) and dist.structure’s :G convention (k_dist = number of functioning components required).
• Deleted R/coherent_system.R (599 lines), R/system_density.R (336 lines), and R/dist.R (118 lines).
• Package shrank from 4312 lines to roughly 2750 lines (~36% reduction) in the R/ directory.

Added

• Imports: dist.structure, algebraic.dist.
• ncomponents re-exported from dist.structure (was a local generic).

kofn 0.2.0

• Generalized masking: loglik_masked() and rdata_masked() extend masked cause-of-failure from series (k=1) to arbitrary k-out-of-m systems.

• Periodic inspection (Scheme 1): loglik_scheme1() and fit_scheme1() support general k via the critical-state density engine.

• Performance: eagerly precomputed critical/functioning states in coherent_system() and vectorized f_sys_general() give ~70x speedup for Scheme 1 likelihood evaluation.

• Migrated optimization to the compositional.mle package. The internal helper multistart_mle() was removed and replaced by a private solve_mle() wrapper around compositional.mle::lbfgsb() with a Nelder-Mead fallback in log-parameterization.

• New vignettes: symmetry-breaking comparison, periodic inspection, observation schemes, general k-out-of-m.

kofn 0.1.0

• Initial release with exponential and Weibull parallel system MLE.
• EM algorithm for Weibull parallel systems.
• Coherent system infrastructure via minimal path/cut sets.
• Fisher information comparison across observation schemes.

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.