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stagelife

stagelife implements the stage life testing (SLT) model of Laumen & Cramer (2019), Naval Research Logistics 66:632-647 – a two-stage life-testing model that unifies progressive censoring with fixed censoring times and step-stress accelerated life testing under the cumulative-exposure model – together with a suite of simulation, estimation, and validation tools.

Features

• 12 baseline lifetime distributions: Weibull, Power Lindley, Exponentiated Lindley, Exponentiated Exponential, Marshall-Olkin Exponential, Lomax, Exponentiated Teissier, Log-Logistic, Chen, Log-normal, Gamma, and Power Muth.
• 3 parameter-sharing cases for the elevated-stage shape parameter: shape1 and shape11 (the paper’s own models) and common (a shared-shape extension).
• Data generation under the random-withdrawal design (rslt()), with both fixed-proportion and fixed-count selection rules; the classical simple-step-stress design is available as a special case.
• Estimation: maximum likelihood via fit_slt(), with standard coef(), vcov(), logLik(), AIC(), BIC(), and confint() methods.
• Inference: asymptotic (Wald) and bootstrap (non-parametric and parametric) confidence intervals, via slt_bootstrap_ci().
• Experimental design: slt_prob_stage1() computes the probability of observing at least one elevated-stage failure, for planning a test.
• Goodness of fit and model comparison: a Kolmogorov-Smirnov test with a parametric-bootstrap correction (slt_gof_ks()), likelihood- ratio tests between nested cases (slt_lrt()), and an AIC/BIC comparison table across fits (slt_model_comparison()).
• Diagnostics: fitted CDF, survival, P-P, and Q-Q plots.
• 4 bundled real step-stress data sets for examples.

Installation

# From the built tarball:
# install.packages("remotes")
remotes::install_local("stagelife_0.1.0.tar.gz")

# Or directly from GitHub:
remotes::install_github("vksharma-bhu/stagelife")

Quick start

library(stagelife)

theta0 <- c(0.05, 1.5); theta1 <- c(0.20, 1)
tau1 <- slt_tau("weibull", theta0, p = 0.5)
d <- rslt(200, "weibull", theta0, theta1, tau1, prop_transfer = 1)

fit <- fit_slt(d, family = "weibull", case = "shape1", tau1 = tau1)
summary(fit)
confint(fit)
plot_cdf(fit)

See vignette("stagelife-intro", package = "stagelife") for the full workflow, including goodness of fit, model comparison, and a real-data example.

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.
Health stats visible at Monitor.