Changes in version 1.0.0 (2026-10-13) This is the first release of epidist on CRAN. epidist estimates epidemiological delay distributions, such as the incubation period or the delay from onset to report, using brms. It corrects for the common biases in these data: interval censoring of the primary and secondary events, right truncation, left truncation, and the dynamical bias from a growing or shrinking epidemic. It provides a naive model, a latent model that samples the unobserved event times, and a marginal model that integrates them out through primarycensored. It also provides an experimental meta model, which fits published summary estimates jointly with individual level data and adjusts each summary for how its study was estimated. Delays can follow a lognormal, gamma, Weibull or generalised gamma distribution. Every distributional parameter can take a brms formula, so delays can vary with covariates, over time or between groups with partial pooling. Tools for preparing data, setting priors, simulating data, summarising and plotting fitted delay distributions, and passing them on to other packages complete the workflow. The meta model is still experimental and its interface may change. New features - Added gengamma(), a generalised gamma delay family in the Prentice parameterisation of flexsurv::dgengamma(), for the naive, latent, marginal and meta models. The Weibull and gamma are special cases and the lognormal is its limit. Closes #644. - epidist_meta_leave_one_out() gains a studies argument that holds out only the studies named, so a model with many studies can be checked against its largest few. - Meta model summary rows of integer date differences are about 30% faster to fit for a gamma delay and 15% faster for a lognormal, with unchanged results. - Meta model summary rows of integer date differences with daily cells and a whole number of days in the primary window are about 1.7 times faster again, with unchanged results. epidist now needs primarycensored 1.6.0 or later. Closes #807. Documentation - The help for epidist_gen_meta_log_lik() and as_epidist_meta_model() now states the cost of log_lik() and loo() for meta model summary rows, and how ndraws reduces it. Closes #705. - Added examples to the simulate_*() functions and to epidist_family(), epidist_formula(), epidist_prior() and epidist_stancode(). - The package description cites the methods it implements. Bug fixes - Removed the remaining lookups of unexported brms functions, so log_lik(), posterior_predict() and posterior_epred() use epidist's own functions for every family. These cover the lognormal, gamma, Weibull, exponential and generalised gamma families. For any other family these functions now give an error. - epidist_meta_leave_one_out() runs the chains of each refit in parallel by default, where they previously ran one after another. Its new cores argument defaults to the mc.cores option where it is set and otherwise to one core per chain. - print() of an epidist_multivariate object writes its header as output rather than a message, so suppressMessages() no longer hides it. Package - The vignettes are built with bookdown::html_vignette2, which cuts the installed size of the package by about 4Mb. - Cited the sierra_leone_ebola_data source by its DOI and corrected its column descriptions. - Removed the unused BH, Rcpp, RcppEigen, pkgdown and usethis suggested dependencies. - epireview is no longer a suggested dependency, so the package needs no repository beyond CRAN. epidist_estimates_epireview() takes any table with the columns epireview uses. Changes in version 0.5.0 This release adds a meta model for fitting to published summary estimates, exponentially growing primary events, left truncation, and a new set of tools for post-processing and plotting fitted models. It also removes several functions and changes some interfaces, as listed below. Breaking changes - predict_delay_parameters() and predict_dpar() are removed in favour of delay_parameter_draws(), and add_mean_sd() in favour of add_summaries(). See #471. - epidist_family_param() and epidist_transform_data() are now internal. Extensions implement epidist_family_model() and epidist_transform_data_model() instead. See #79. - The is_epidist_*() predicates share one signature, is_epidist_(data), and no longer take .... Closes #706. - epidist data objects share an epidist_data class, checked by is_epidist_data(). They re-check themselves when modified and drop any class whose requirements they no longer meet, with a warning. See ?epidist_data and #399. - cmdstanr is no longer a suggested dependency. Tests and examples fit through rstan, and cmdstanr remains available as a brms backend. See #687 and #688. - Now requires R 4.1.0, brms 2.23.0 and primarycensored 1.5.2. The Remotes field is removed, so all dependencies resolve from CRAN. See #592 and #727. New features - Added the meta model, as_epidist_meta_model(), which fits published summary estimates jointly with individual level data. Each summary is forward modelled from the study's own estimation procedure, so estimates that did not adjust for censoring or truncation still contribute unbiased information. It is experimental and its interface may change. See #620. - Added as_epidist_estimates_data(), epidist_estimates_summaries(), epidist_estimates_parameters(), epidist_estimates_epireview() and as_epidist_multivariate() for preparing published estimates. They cover means, standard deviations, quantiles, standard errors, fitted distribution parameters and summaries with a covariance, and check the inputs for common problems. See #620. - Added epidist_gen_meta_log_lik() and epidist_gen_meta_predict(), so log_lik(), loo() and posterior predictions work for meta model fits. See #620. - Added epidist_meta_leave_one_out(), which refits a meta model once per study with that study held out and reports how the delay mean and standard deviation change. Closes #642. - Added simulate_study(), which applies a published study's observation and estimation procedure to a simulated line list. Closes #672. - The meta model can estimate the growth rate of a study from NA or uncertain growth_rate values, sharing it with individual level data. Closes #678. - Added an exponentially growing primary event distribution with primary = "expgrowth" for the latent, marginal and meta models. The growth rate is a distributional parameter, so it takes a formula and prior. See #489 and #618. - Added left truncation through a delay_min argument to as_epidist_marginal_model(), also supported by the meta model. See #588 and #596. - Added delay_parameter_draws(), add_delay_parameter_draws(), add_summaries(), epidist_strata() and delay_summary_draws() for posterior draws of the delay distribution and its mean, standard deviation and quantiles. epidist_newdata() builds the newdata they need. See #280, #471 and #667. - Added plot_events(), plot_delays(), and plot() and ggplot2::autoplot() methods for delay draws. plot_delays() also gives a posterior predictive check of a fitted model. See #670, #689 and #743. - Added a distspec::as_dist_spec() method for fitted models. See #712. - Added simulate_dates(), which turns simulated event times into censored dates. - Exported epidist_gen_log_lik(), and made its generic method linear in the number of posterior draws. See #79, #476 and #646. - epidist_prior() no longer warns about user priors on valid brms parameters, and lists unmatched priors clearly. See #483. - The package lifecycle is now maturing rather than experimental. The meta model is still experimental. See #781. Bug fixes - Added a missing Jacobian adjustment to the latent model for observations whose primary and secondary windows overlap. See #606. - epidist() now restores the PKG_CPPFLAGS and PKG_LIBS environment variables that rstan leaves set. See #532. - The generic epidist_gen_log_lik() method now normalises over delay_min when there is no right truncation. Closes #646. - delay_parameter_draws() no longer passes on the brms warning about the infinite observation times epidist uses. Closes #718. - Delay draws keep their class through common dplyr verbs, so plot() still dispatches. Closes #721. - The meta model log likelihood no longer advances the RNG stream. Closes #750. - Removed calls to unexported brms functions. See #420. Documentation - Added vignettes on the meta model, applied to published Ebola estimates, on left truncation, and on extending epidist. See #596 and #620. - All vignettes that fit models are now precomputed, so they ship with the package without needing a model fit at build time. See #619 and #688. - Reworked the getting started vignette around the package's simulation and plotting tools. See #736. - Added the meta model to the model guide vignette. See #620 and #709. - Documented the return value of every exported function, and installing from CRAN and r-universe in the README. See #702. Changes in version 0.4.1 Bug fixes - Fixed Stan compilation failure with primarycensored >= 1.4.0 by adding the new L (left truncation) parameter to the primarycensored_lpmf call in the marginal model. See #583. - Added primarycensored (>= 1.4.0) version bound to DESCRIPTION. - Updated test expectations for changed primarycensored error handling. - Re-enabled approximate inference vignette evaluation using dev brms with pathfinder path fix. See #579. Package - Load only required primarycensored Stan functions (primarycensored_lpmf and ODE/distribution helpers) with pcd_load_stan_functions(dependencies = TRUE) instead of loading all functions. See #582. CI - Extended check-cmdstan workflow to also check marginal model Stan syntax. Changes in version 0.4.0 Package - Enforce line length and use cli for latent prior checks. See #580. - Removed CodeDepends from DESCRIPTION dependencies. Documentation - Restructured pkgdown reference with higher-level categories. See #574. - Updated FAQ to recommend pp_check with expanded data. See #575. - Clarified weight parameter documentation in as_epidist_marginal_model(). See #565. - Fixed pathfinder parameter usage in approximate inference vignette. See #573. Changes in version 0.3.1 Hotfix release to patch a change in how the grepl function works in new versions of R. Changes in version 0.3.0 This release adds support for a wider range of distributions in the marginal model, improves documentation with new vignettes and FAQ sections, enhances the getting started guide with clearer examples of model comparison, and fixes several bugs related to parameter bounds and likelihood calculations. Models - Added Stan-side support for fitting all distributions supported by primarycensored in the marginal model. See #540. - Added R-side analytical likelihood support for Lognormal, Gamma, and Weibull distributions. See #540. Package - Remove caching of vignettes. See #533. Documentation - Added a new vignette "Guide to the statistical models implemented in epidist". See #514. - Added a new FAQ section showcasing how to use the posterior package with epidist models, particularly for working with random variables (rvars) to propagate uncertainty in calculations. See #547. - Added a new FAQ section on how to use the marginaleffects package with epidist models. See #547. - Reduced the focus on simulating data in the getting started vignette to make it more accessible. See #549. - Made the entry to the package friendlier with clearer examples and improved documentation. See #549. - Added a schematic to explain right truncation more clearly to the getting started vignette. See #549. - Added a comparison of fitting naive and marginal models in the getting started vignette to highlight the importance of accounting for biases. See #549. - Added examples showing how to extract estimated parameters and plot them against true values to evaluate model performance. See #549. Bugs - Fixed a vector length issue for censoring that was causing problems in some likelihood calls. See #540. - Fixed a bug in the preprocessing of the Weibull family. See #540. - Fixed a bug where bounds were not set for mu parameters in custom families. See #549. - Fixed a bug in predict_delay_parameters() where it couldn't detect brms families when used directly. See #549. Changes in version 0.2.0 This release adds a new marginal model based on primarycensored which provides a more efficient approach for fitting delay distributions compared to the existing latent model. We've also improved data handling by adding support for aggregated data across all models, added comprehensive examples using real world data, and enhanced documentation based on user feedback. The package has also undergone significant internal improvements including generalised Stan reparameterisation and improved data transformation methods. As part of this release we have moved from @athowes maintaining the package (who led the initial package development, implementation of the S3 infrastructure, implementation of the core models, and wrote the first versions of the getting started vignette, Ebola case study, FAQ section, and the approximate inference vignette) to @seabbs maintaining the package. Models - Added a marginalised likelihood model based on primarycensored. This can be specified using as_epidist_marginal_model(). This is currently limited to Weibull, log-normal, and gamma distributions with uniform primary censoring but this will be generalised in future releases. See #426. - Added user settable primary event priors to the latent model. See #474. - Added a marginalised likelihood to the latent model. See #474. - Added a weight argument to as_epidist_marginal_model() to allow for weighted data (for example count data) to be used in the marginal model. See #509. - Added a epidist_aggregate_data method to as_epidist_marginal_model() to allow straightforward use of the marginal model with aggregated data. See #510. - Added a epidist_aggregate_data method to as_epidist_latent_model() to allow straightforward use of the latent model with aggregated data. See #510. - Added a epidist_aggregate_data method to as_epidist_naive_model() to allow straightforward use of the naive model with aggregated data. See #510. - Updated the naive model to internally transform the data to be optimally aggregated as for the marginal model. See #510. Package - Remove the default method for epidist(). See #473. - Added enforce_presence argument to epidist_prior() to allow for priors to be specified if they do not match existing parameters. See #474. - Added a merge argument to epidist_prior() to allow for not merging user and package priors. See #474. - Generalised the Stan reparametrisation feature to work across all distributions without manual specification by generating Stan code with brms and then extracting the reparameterisation. See #474. - Added a transform_data S3 method to allow for data to be transformed for specific models. This is specifically useful for the marginal model at the moment as it allows reducing the data to its unique strata. See #474. - Added new epidist_aggregate_data class to handle pre-aggregated line list data. See #510. - Added a as_epidist_aggregate_data() method for epidist_linelist_data objects to allow for easy conversion to aggregate data. See #510. - Added a as_epidist_linelist_data() method for epidist_aggregate_data objects to allow for easy conversion to linelist data. See #510. - Added an example dataset sierra_leone_ebola_data to the package. See #510. - Added examples to most functions to show usage of the package. See #510. - Added improved documentation explaining how the epidist_transform_data() methods work for the marginal and naive models. See #510. Documentation - Brings the README into line with epinowcast standards. See #467. - Switched over to using the marginal model as default in the documentation. See #426. - Added a helper functions for new variables to avoid code duplication in vignettes. See #426. - Improved the Ebola case study vignette to use truncated data and to reduce the focus on exploratory data analysis. See #510. Bugs - Switched to using a patched of primarycensored that doesn't make use of size(). This fixes some Mac compilation edge cases. See #524. Changes in version 0.1.0 This is the first minor release of epidist intended for early test users of the package. As some features may change, the package is marked as experimental. We expect to release a stable 1.0.0 version shortly. The epidist package implements models for epidemiological delay distributions. It uses brms to perform Bayesian inference. One data format is currently available: 1. The linelist data format Two statistical models are currently available: 1. The naive model: which models the delay directly using brms 2. The latent model: which implements a latent variable model to correct for biases in the data The package is readily extensible to additional models via an S3 class based system. In particular, model fitting with [epidist()] is possible using S3 classes for custom: 1. Families 2. Formula 3. Prior distributions 4. Stan code We provide functionality for post-processing. Alternatively, users may directly use tidybayes for specific families. Three vignettes are available. There is also a frequently asked questions section.