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Changelog

Source: NEWS.md

shewhartr 1.4.0

New features: reproducing Ferraz et al. (2020) (GitHub issues #2, #3)

  • shewhart_regression() gains limits_scale = c("original", "model"). With "model", sigma comes from the moving ranges of the residuals on the transformed scale of the model’s left-hand side, the band g_hat +- 3 sigma is formed there and back-transformed: for model = "log" the multiplicative, asymmetric bands of Perla et al.
    1. and Ferraz et al. (2020), whose lower limit never falls below
    1. .sigma is then on the model scale, the new columns .model_value / .model_center hold what the runs rules are applied to, and the rules run on that scale. For linear, Gompertz and logistic models both options coincide. The default is unchanged.
  • User formulas whose left-hand side is log(), log10(), log2(), log1p() or sqrt() of the response (plus a constant, optionally in I()) now have their fitted values back-transformed to the scale of the data; previously the centre line stayed on the model scale.
  • monitor() on a regression chart honours the stored limits_scale and lower_bound (both now kept in metadata), so Phase II limits are exactly the constructor’s forward projection of the last phase.
  • shewhart_regression(phase_changes = integer(0)) fits a single phase without detection and needs only 3 observations, so a prospective replay can calibrate one phase at a time with calibrate() and judge the following days with monitor().
  • "log", "loglog" and "auto" (when it picks log) stop with a clear error naming the first negative value instead of producing NaN limits; also in monitor().
  • .phase_label of a regression chart with a Date (or date-time) index carries the end of each phase: “Base (until 2020-05-11)”, “Phase 1 (until 2020-05-18)”, …, “Monitoring” (pt “até”, es “hasta”, fr “jusqu’au”).
  • autoplot() for regression charts gains phase_dates (NULL: automatic for a date index; TRUE / FALSE force it) and legend_position = c("top", "inside"); "inside" stacks the legend in the top-left corner of the panel, as in the articles’ figures. Dated labels at the top wrap to rows of three.
  • New dataset cvd_brazil: daily new COVID-19 deaths for Brazil, Pernambuco and Sao Paulo, 2020-02-25 to 2020-12-31, from Wesley Cota’s covid19br compilation of the Ministry of Health bulletins. The raw values are kept, including one PE correction of -37 deaths on 2020-09-03.

New vignettes (closes #2, #3)

  • vignette("article-charts"): reproduces the charts of Ferraz et al. (2020, SBPO and Revista Brasileira de Estatistica) – the unadapted individuals chart, Brazil and Recife with the articles’ phases (legend identical to the figures) and with automatic detection, Pernambuco and Sao Paulo, and the “Monitoramento” segment as a calibrate() + monitor() projection – with a table of what differs from the originals (closes #2).
  • vignette("prospective-replay"): replays the articles’ “simulation” of prospective monitoring day by day with calibrate() / monitor() (frozen limits and daily refits), compares the phase dates with the articles’ and with phase_rule, and adds a Monte Carlo study of the strategy on Poisson counts with known change points: spurious phases, detection delays, and the in-control ARL of the seven- and nine-point rules against 2^k - 1 (closes #3).

Bug fixes (audit of 2026-09-25)

  • shewhart_capability() on Xbar-R / Xbar-S charts no longer multiplies the chart’s sigma by sqrt(n) (it is already the per-individual sigma), and computes the mean and Pp/Ppk from the individual measurements instead of the subgroup means. Cp was depressed by sqrt(n) and Pp could be Inf. Subgroup charts now carry their individual measurements in metadata$values (#2).
  • shewhart_capability() bootstrap intervals re-estimate sigma within in every replicate with the chart’s own estimator (whole subgroups resampled for Xbar charts, consecutive pairs for individual charts). The Cp/Cpk interval used to be an interval for Pp/Ppk. Capability now errors for chart types where it is undefined (attribute, regression, multivariate) (#24).
  • monitor() on an I-MR chart now returns the moving-range columns (.mr, seeded with the last Phase I value, and the stored MR limits), so autoplot() and as_plotly() work on Phase II I-MR charts (#3).
  • p / c / u charts with exact limits (limits = "binomial" / "poisson") flag Nelson 1 against the plotted exact limits, not against 3 sigma; monitor() keeps the exact method instead of falling back to 3-sigma limits (#10).
  • Regression chart legend wraps to rows of five keys when there are more than five phases, with the title above the keys, so it no longer runs off a 7-inch device; as_plotly() places the regression legend below the plot (#12, GitHub issue #1).
  • Nelson rules 3, 4, 7 and 8 no longer abort on missing values: a window containing an NA does not fire (#14).
  • glance()$pct_violations is now the share of points flagged by at least one rule (mean(.flag_any)) and can no longer exceed 1 (#17).
  • tidy() on a regression chart follows the documented chart / line / value schema (long format, with .phase and endpoint columns) (#18).
  • as_plotly() forwards locale, show_violations and show_sigma_zones to autoplot() (#19).
  • show_sigma_zones = TRUE now draws the 1- and 2-sigma zones on the top panel of I-MR, Xbar-R and Xbar-S plots (#20).
  • Nelson rules 5 and 6 fire at the point that completes the pattern (which must itself be beyond the zone): the same pair is no longer flagged twice, and patterns starting at positions 1-2 are caught (#30).
  • shewhart_p() and monitor() reject subgroups with n = 0 instead of silently producing NaN proportions (#32).
  • The regression legend uses the phase labels the constructor computes (“Base”, “Phase 1”, …, “Monitoring”); the regression subtitle and the CUSUM “Positive” / “Negative” legend are translated through the locale table (#36).

Release hygiene

  • lubridate and vdiffr removed from Suggests (unused).
  • inv_box_cox() gains an example; cran-comments.md describes the 1.3.0 submission.
  • Plot chunks re-enabled in the phase1-phase2, getting-started, variables-charts, attributes-charts, diagnostics and box-cox vignettes (#37).

Bug fixes: regression chart and calibrate() (audit 2026-09-25)

  • monitor() on a regression chart no longer restarts the within-phase position .N at 1: Phase II continues from the last position of the last Phase I phase, so an in-control continuation is predicted on the extrapolated trend instead of the start of the phase (audit #1). The last-phase .N is stored in metadata$phase_n_end.
  • monitor() on a regression chart now uses the residual sigma of the last phase (the phase whose fit it extrapolates), stored in metadata$phase_sigma, instead of the median sigma across phases (audit #11). sigma_hat of the Phase II object is that sigma.
  • A phase with fewer than 3 observations now extrapolates the previous phase’s fit (continuing .N) and inherits its sigma, instead of restarting the previous curve at .N = 1 with a sigma estimated from 1-2 residuals. A NULL fit no longer deletes its slot in $fits, which shifted every later phase (audit #34).
  • calibrate(trim_outliers = TRUE) now trims a running copy of the data, so violation positions of a trimmed fit are mapped to the rows that fit was built on. Previously an observation dropped in one iteration could come back in the next and the loop oscillated until max_trim_iter. Subgrouped charts (Xbar-R, Xbar-S, subgrouped Hotelling) drop whole subgroups instead of individual rows, which used to abort with “unequal sizes” (audit #4).
  • shewhart_regression(start_base = ) is no longer ignored when phase_changes is supplied. start_base now defaults to NULL: 10 with automatic detection; with phase_changes, the base phase ends at the first supplied change unless start_base is given explicitly, in which case it adds a cut (audit #21).
  • model = "auto" no longer maps a square-root Box-Cox lambda (~0.5) to "loglog", a transform stronger than log. Lambda is rounded to the nearest rung the menu offers: < 0.25 gives "log", anything else "linear". Rounding also removes the floating-point asymmetry that treated lambda = -0.1 and 0.1 differently. The covid-recife and box-cox vignettes are corrected accordingly (audit #22).
  • Gompertz / logistic regression charts: the first fitted increment of each phase no longer carries the +1 offset of the cumulative fit (cumsum(y) + 1); increments are C(.N) - C(.N - 1) with C(0) = 1 (audit #35).
  • Gompertz() now includes the factor e of the Zwietering et al.
    1. parameterisation, so k is the maximum slope and lag the tangent intercept, as documented. Previous curves had maximum slope k / e (audit #26).
  • Documented in-control ARL of the phase rules corrected from 64 / 256 to 127 / 511 (2^k - 1 for a run of k same-side points) in ?shewhart_regression and the regression-charts and arl-simulation vignettes (audit #27).
  • covid-recife vignette: death-count limits are now clipped with lower_bound = 0, and the Perla et al. (2020) and Ferraz et al.
    1. citations now match the published papers (audit #25).
  • Removed the R CMD check NOTE “no visible binding for global variable ‘.phase’” (audit #31).

Bug fixes: memory-based and multivariate charts (audit 2026-09-25)

  • shewhart_mcusum(): the default decision intervals (k = 0.5) held ARL_0 ~ 200 only for p = 2; with the old table ARL_0 was ~140 at p = 3 and ~85 at p = 5. The table for p = 2..10 was re-derived by Monte Carlo (dev/calibrate-h-tables.R, 20,000 paths per cell); p = 2 reproduces Crosier’s 5.50 (5.48). Default h is larger for every p > 2 (finding 5).
  • shewhart_mewma(): the default h table was wrong for p >= 3 (ARL_0 ~136 at lambda = 0.1, p = 4) and was a steady-state table used with the time-varying default. There are now two simulated tables, one per covariance mode, and the lookup follows steady_state (finding 6).
  • shewhart_ewma(): default L is now 2.86, which with lambda = 0.2 gives ARL_0 ~ 370 as documented; the old L = 2.7 gave ~240 (finding 7).
  • shewhart_ewma() / monitor(): runs-rule flags now fire exactly at the plotted limits for any L (the sigma-equivalent was inverted, placing the alarm at 9 se / L). Zones for rules 5-8 are thirds of the limit width; this is documented (finding 8).
  • shewhart_xbar_r(), shewhart_xbar_s(), subgrouped shewhart_hotelling() and their monitor() counterparts keep subgroups in order of first appearance instead of sorting labels (S1, S10, S11, S2, ...), which scrambled runs rules and the x axis (finding 9).
  • shewhart_ewma(), shewhart_cusum() and their monitor() methods now reject missing values; a single NA used to switch off every later alarm silently (finding 13).
  • monitor() on an MCUSUM chart stores the final S vector, so chained Phase II batches continue the accumulator (finding 15).
  • monitor() on an MEWMA chart continues Z from the last Phase I (or previous Phase II) value with the matching covariance, instead of restarting at 0 (finding 16).
  • Subgrouped shewhart_hotelling() and its monitor() keep a Date (or other classed) index instead of turning it numeric (finding 29).
  • monitor() on an Xbar-S chart fitted with sigma_method = "pooled_sd" and unequal subgroup sizes no longer warns on every call that sizes differ from the (average) Phase I size (finding 33).

shewhartr 1.3.0

CRAN release: 2026-05-13

New chart family

The multivariate side of the package now has the natural pair of memory-based charts. Both follow the calibrate() / monitor() Phase I / Phase II workflow.

  • shewhart_mewma() — Multivariate Exponentially Weighted Moving Average (Lowry, Woodall, Champ & Rigdon 1992). The multivariate analogue of shewhart_ewma(): joint monitoring of p > 1 correlated variables for small persistent shifts in the vector mean. Time-varying and steady-state covariance both supported. Decision interval h calibrated by lookup in Prabhu & Runger
    1. Table 3 (ARL_0 ~ 200).
  • shewhart_mcusum() — Multivariate CUSUM (Crosier 1988). The multivariate analogue of shewhart_cusum(). Uses Crosier’s shrinkage operator: at each step the cumulative vector is shrunk towards zero by k / C_i where C_i is its Mahalanobis norm; if the norm falls below k, the cumulative vector resets to zero. Decision interval h calibrated by lookup in Crosier (1988) Table 1 for k = 0.5, ARL_0 ~ 200, p = 2..10. Phase II monitoring continues from the calibration’s final S vector (Crosier 1988 §5).

Visual identity

  • Every autoplot() method now uses shewhart_palette() and shewhart_theme(), so plots from any chart family share the same editorial look (off-white surface, single horizontal grid, bold left-aligned title, sequential phase palette, hollow firebrick rings on out-of-control points). Out-of-control marks centralised in a new internal violation_layers() helper, sized at halo 1.7 / ring 1.4 / stroke 0.7.
  • Regression chart legend title is now plural and bold (“Phases” / “Fases”) and uses localised Phase 0, Phase 1, … labels via the phase_n and new legend_phases locale entries.
  • The arl-simulation vignette’s hand-rolled chart was using theme_minimal() with default ggplot2 colours; now uses shewhart_theme() and the package palette so it matches the rest.

Bug fixes / hygiene

  • Three U+2014 em-dash characters in R/autoplot.R (two comments, one string literal) replaced with ASCII alternatives or the — escape so R CMD check no longer warns about non-ASCII source.

shewhartr 1.2.0

This release closes the remaining items from dev/ROADMAP.md §11 that were left for after v1.1: a plotly bridge and external numerical validation against the long-established qcc package.

Interactive plots: as_plotly()

  • New generic as_plotly() with a shewhart_chart method that converts any chart into an interactive plotly figure. For two-panel charts (I-MR, X̄-R, X̄-S) the helper produces a plotly::subplot() with a synchronised x-axis. plotly is in Suggests, so it is only loaded on demand.
  • The tooltip argument is forwarded to plotly::ggplotly() for full control of what hover boxes display.

Validation against qcc

  • New tests/testthat/test-vs-qcc.R (skipped silently if qcc is not installed) compares the limits computed by shewhartr to the reference values from the qcc package on its canonical example datasets — pistonrings for the variables charts, orangejuice for p / np, circuit for c. Every centre line and 3-sigma limit agrees with qcc to within 1e-3 absolute tolerance.

Test hygiene

  • test-monitor.R no longer triggers the (correct) “small c_bar” cli_warn from chart-c.R: the test data uses lambda = 12 so the normal approximation is well-behaved. The 1-warning warning in devtools::test() is gone; the suite is now FAIL 0 / WARN 0.

shewhartr 1.1.0

This release closes most of the items left open in dev/ROADMAP.md §11.

New chart family: multivariate

  • shewhart_hotelling() is the package’s first multivariate chart — a Hotelling T² chart for jointly monitoring p > 1 correlated variables. Both individual observations (subgroup = NULL) and subgrouped data are supported, with the appropriate exact Phase I limits (Beta for individuals, F for subgroups) and the slightly wider Phase II limits as derived in Tracy, Young & Mason (1992) and Montgomery (2019, Chapter 11). The implementation follows Mason & Young (2002).
  • The augmented tibble carries the T² statistic per row, its decomposition by variable (the contribution of each variable to the alarm — useful when T² signals but no univariate chart does), and a logical flag against the appropriate chart-level UCL.
  • Vignette multivariate-charts walks through the standard worked example: a chemical process with three correlated quality characteristics, showing how the multivariate chart catches a correlation-breaking shift that any of the three univariate charts would miss.

Phase II for EWMA and CUSUM

  • monitor() now dispatches to monitor_ewma() and monitor_cusum() (R/calibrate.R), so the calibrate(..., chart = "ewma") / monitor(new_data, calib) workflow now works uniformly across every chart in the package — not just the Shewhart-style ones.
  • calibrate() accepts the new keys "ewma", "cusum", "hotelling".

Bug fixes

  • SSgompertzDummy self-starter is more robust: starting values for b2 and b3 are now derived from the cumulative-mid-point heuristic rather than hard-coded constants, fixing the convergence failure with typical sample sizes that previously required \dontrun{} in the example.

shewhartr 1.0.0

This release is a comprehensive reposition of the package. The original (v0.1.x, distributed as Shewhart) was COVID-focused and provided a single function family for regression-based control charts. v1.0.0 is a full general-purpose SPC toolkit while preserving the regression-chart speciality that motivated the package.

Rename. As part of the reposition, the package has been renamed Shewhart → shewhartr to follow modern lowercase R-package conventions and to free the name “Shewhart” for the methodology in text and documentation. Update existing code with library(shewhartr) (formerly library(Shewhart)).

The API has been substantially redesigned. Existing scripts written against v0.1.x will not run unchanged.

Repositioning

  • The package is now a general-purpose SPC toolkit. The COVID-19 use case is preserved as a vignette case study (covid-recife), not as the organising principle.
  • The package competes in the same space as qcc and qicharts2, and emphasises five differentiators: tidyverse-native API, broom integration, regression-based charts as a first-class citizen, embedded methodology (ARL, Box-Cox, runs tests), and an explicit Phase I / Phase II workflow.

New chart families

  • Variables: shewhart_i_mr(), shewhart_xbar_r(), shewhart_xbar_s().
  • Attributes: shewhart_p(), shewhart_np(), shewhart_c(), shewhart_u(). The c and u charts accept limits = "poisson" for exact Poisson quantile limits rather than the normal approximation.
  • The flagship shewhart_regression() replaces the old shewhart() function with a cleaner API, an extensible model menu (auto, linear, log, loglog, gompertz, logistic, plus user formulas), automatic phase detection via configurable runs rules, and proper handling of irregular time grids.
  • Memory-based charts: shewhart_ewma() (Roberts 1959) for the Exponentially Weighted Moving Average chart, with both time-varying and steady-state limits, and shewhart_cusum() (Page 1954) for the two-sided tabular CUSUM chart with configurable reference value k and decision interval h. Both fit in the same S3 / broom / autoplot pipeline as the classical charts.

New methodology

  • shewhart_runs() implements the eight Nelson rules (1984, 1985) plus a Western Electric “7 in a row” variant for backward compatibility. Rule sets are user-configurable on every chart.
  • shewhart_arl() performs Monte Carlo Average Run Length simulation for arbitrary rule combinations.
  • shewhart_box_cox() returns the profile log-likelihood, optimal lambda, and 95% CI in the Box & Cox (1964) tradition.
  • shewhart_diagnostics() produces a five-panel Tukey-style residual diagnostic display.
  • shewhart_capability() computes Cp/Cpk/Pp/Ppk with bootstrap confidence intervals.
  • calibrate() and monitor() provide an explicit Phase I / Phase II workflow.

S3 / broom integration

  • All charts return an S3 object of class shewhart_chart with a specific subclass.
  • print(), summary(), autoplot(), tidy(), glance() and augment() methods are provided for every chart type.

Internationalisation

  • All user-facing chart functions accept a locale argument ("en", "pt", "es", "fr") that controls plot labels and informative messages. Validation errors remain in English to facilitate cross-user debugging.

Developer-facing changes

  • Depends collapsed: the package no longer depends on the entire tidyverse meta-package or on tibbletime/pals/scales. The new Imports are minimal and explicit.
  • plotly moved to Suggests to avoid pulling a heavy dependency for users who don’t need interactive plots.
  • All input validation uses cli::cli_abort() / cli::cli_warn() with multi-line, informative messages.
  • .onAttach() no longer prints a banner.
  • New data-raw/build_all.R script generates six synthetic datasets (tablet_weight, bottle_fill, pcb_solder, claims_p, temperature_drift, bacterial_growth).
  • New documentation site built with pkgdown at https://castlaboratory.github.io/shewhartr/. Ten topical articles, including a dedicated memory-based-charts vignette covering EWMA, CUSUM and the trade-offs versus Shewhart-style charts.

Breaking changes (full list)

  • shewhart() (the plotting function) has been removed. Use shewhart_regression() followed by autoplot().
  • shewhart_fit() is no longer exported. Use shewhart_regression().
  • shewhart_model() is no longer exported. Use shewhart_regression().
  • shewhart_7points() is no longer exported. Use shewhart_runs(rule = "we_seven_same") for the same behaviour, or the recommended shewhart_runs(rule = "nelson_2_nine_same").
  • The default phase-detection rule is now Nelson 2 (9 points same side; ARL_0 ~ 256), not the legacy 7-points-same-side (ARL_0 ~ 64). Pass phase_rule = "we_seven_same" to recover the old behaviour.
  • The package banner printed on .onAttach() has been removed.
  • All output column names follow broom-style with a leading . (.fitted, .upper, .lower, .flag_*).