# mfrmr Visual Diagnostics

This vignette is a compact map of the main base-R diagnostics in `mfrmr`. It is organized around four practical questions:

- How well do persons, facet levels, and categories target each other?
- Which observations or levels look locally unstable?
- Is the design linked well enough across subsets or forms?
- Where do residual structure and interaction screens point next?

All examples use packaged data and `preset = "publication"` so the same code is suitable for manuscript-oriented graphics.

If you are selecting figures for a report, use `reporting_checklist()` before or alongside this vignette. Its `"Visual Displays"` rows now mirror the public plotting family shown here.

## Minimal setup

    library(mfrmr)

    toy <- load_mfrmr_data("example_core")

    fit <- fit_mfrm(
      toy,
      person = "Person",
      facets = c("Rater", "Criterion"),
      score = "Score",
      method = "JML",
      model = "RSM",
      maxit = 20
    )

    diag <- diagnose_mfrm(fit, residual_pca = "none")
    checklist <- reporting_checklist(fit, diagnostics = diag)
    subset(
      checklist$checklist,
      Section == "Visual Displays",
      c("Item", "Available", "NextAction")
    )

## 1. Targeting and scale structure

Use the Wright map first when you want one shared logit view of persons, facet levels, and step thresholds.

    plot(fit, type = "wright", preset = "publication", show_ci = TRUE)

Interpretation:

- Compare person density on the left to facet and step locations on the right.
- Large gaps suggest weaker targeting in that logit region.
- Wide overlap in confidence whiskers means neighboring levels are not cleanly separated.

Next, use the pathway map when you want to see how expected scores progress across theta.

    plot(fit, type = "pathway", preset = "publication")

Interpretation:

- Steeper rises indicate stronger score progression.
- Dominant-category strips show where each category is most likely to govern the score.
- Flat or compressed regions suggest weaker category separation.

## 2. Local response and level issues

Unexpected-response screening is useful for case-level review.

    plot_unexpected(
      fit,
      diagnostics = diag,
      abs_z_min = 1.5,
      prob_max = 0.4,
      plot_type = "scatter",
      preset = "publication"
    )

Interpretation:

- Upper corners combine large residual mismatch with low model probability.
- Repeated appearances of the same persons or levels are more informative than a single extreme point.

Displacement focuses on level movement rather than individual responses.

    plot_displacement(
      fit,
      diagnostics = diag,
      anchored_only = FALSE,
      plot_type = "lollipop",
      preset = "publication"
    )

Interpretation:

- Large absolute displacement indicates stronger tension between observed data and current calibration.
- For anchored runs, this is especially useful as an anchor-robustness screen.

### Strict marginal follow-up

When you need the package’s latent-integrated follow-up path, switch to `MML` and request `diagnostic_mode = "both"` so the legacy and strict branches stay visible side by side. The chunk below uses compact quadrature for optional local execution; final reporting should be refit with the package default or a higher quadrature setting.

    fit_strict <- fit_mfrm(
      toy,
      person = "Person",
      facets = c("Rater", "Criterion"),
      score = "Score",
      method = "MML",
      model = "RSM",
      quad_points = 7,
      maxit = 40
    )

    diag_strict <- diagnose_mfrm(
      fit_strict,
      residual_pca = "none",
      diagnostic_mode = "both"
    )

    strict_checklist <- reporting_checklist(fit_strict, diagnostics = diag_strict)
    subset(
      strict_checklist$checklist,
      Section == "Visual Displays" &
        Item %in% c("QC / facet dashboard", "Strict marginal visuals"),
      c("Item", "Available", "NextAction")
    )

    plot_marginal_fit(
      diag_strict,
      top_n = 12,
      preset = "publication"
    )

Interpretation:

- Treat strict marginal plots as exploratory corroboration screens, not as standalone inferential tests.
- Use the checklist rows to confirm that the current run actually supports the strict branch before routing figures into a report.
- When pairwise follow-up is needed, continue with `plot_marginal_pairwise(diag_strict, preset = "publication")`.

## 3. Linking and coverage

When the design may be incomplete or spread across subsets, inspect the coverage matrix before interpreting cross-subset contrasts.

    sc <- subset_connectivity_report(fit, diagnostics = diag)
    plot(sc, type = "design_matrix", preset = "publication")

Interpretation:

- Sparse rows or columns indicate weak subset coverage.
- Facets with low overlap are weaker anchors for cross-subset comparisons.

If you are working across administrations, follow up with anchor-drift plots:

    drift <- detect_anchor_drift(current_fit, baseline = baseline_anchors)
    plot_anchor_drift(drift, type = "heatmap", preset = "publication")

## 4. Residual structure and interaction screens

Residual PCA is a follow-up layer after the main fit screen.

    diag_pca <- diagnose_mfrm(fit, residual_pca = "both", pca_max_factors = 4)
    pca <- analyze_residual_pca(diag_pca, mode = "both")
    plot_residual_pca(pca, mode = "overall", plot_type = "scree", preset = "publication")

Interpretation:

- Early components with noticeably larger eigenvalues deserve follow-up.
- Scree review should usually be paired with loading review for the component of interest.

For interaction screening, use the packaged bias example.

    bias_df <- load_mfrmr_data("example_bias")

    fit_bias <- fit_mfrm(
      bias_df,
      person = "Person",
      facets = c("Rater", "Criterion"),
      score = "Score",
      method = "MML",
      model = "RSM",
      quad_points = 7
    )

    diag_bias <- diagnose_mfrm(fit_bias, residual_pca = "none")
    bias <- estimate_bias(fit_bias, diag_bias, facet_a = "Rater", facet_b = "Criterion")

    plot_bias_interaction(
      bias,
      plot = "facet_profile",
      preset = "publication"
    )

Interpretation:

- Facet profiles are useful for seeing whether a small number of levels drives most flagged interaction cells.
- Treat these plots as screening evidence; confirm with the corresponding tables and narrative reports.

## 5. Secondary visual layer

The package ships a second-wave visual layer for teaching and diagnostic follow-up. These helpers are not default reporting figures; use them after the main screens above.

- `plot_guttman_scalogram(fit, diagnostics)` renders a person x facet-level response matrix with an unexpected-response overlay, for teaching-oriented scalogram intuition and local triage.
- `plot_residual_qq(fit, diagnostics)` plots a Normal Q-Q of person-level standardized residual aggregates as exploratory follow-up on residual tail behavior.
- `plot_rater_trajectory(list(T1 = fit_a, T2 = fit_b))` tracks rater severity across named waves. The helper does not perform linking; supply waves that have already been placed on a common anchored scale (see `vignette("mfrmr-linking-and-dff")`) before interpreting movement as rater drift.
- `plot_rater_agreement_heatmap(fit, diagnostics)` renders a compact pairwise rater x rater agreement matrix; pass `metric = "correlation"` to colour by the Pearson-style `Corr` column instead of exact agreement.

## Recommended sequence

For a compact visual workflow:

1. `reporting_checklist()` when you want the package to route which figures are already supported.
2. `plot_qc_dashboard()` for one-page triage.
3. `plot_unexpected()`, `plot_displacement()`, `plot_marginal_fit()`, and `plot_interrater_agreement()` for local follow-up.
4. `plot(fit, type = "wright")` and `plot(fit, type = "pathway")` for targeting and scale interpretation.
5. `plot_residual_pca()`, `plot_bias_interaction()`, and `plot_information()` for deeper structural review.
6. `plot_guttman_scalogram()`, `plot_residual_qq()`, `plot_rater_trajectory()`, and `plot_rater_agreement_heatmap()` as the teaching / drift / agreement-heatmap follow-up layer.

## Related help

- `help("mfrmr_visual_diagnostics", package = "mfrmr")`
- `help("mfrmr_workflow_methods", package = "mfrmr")`