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Plot a differential-functioning interaction grid

Source: R/api-plotting-dispatch.R
plot.mfrm_dif_interaction.Rd

Display saved residual means by facet level and group. This is a descriptive screen for follow-up; residual differences do not isolate differential functioning.

Usage

# S3 method for class 'mfrm_dif_interaction'
plot(x, type = "heatmap", ...)

Arguments

x

A result from dif_interaction_table().

type

The sole view, "heatmap".

...

Heatmap controls below, plus draw = FALSE to return data without drawing. This input accepts metric = "obs_exp" or "t"; "contrast" requires a result from analyze_dff().

Value

An mfrm_plot_data object with data$matrix, data$pairs, the selected metric and retained interpretation notes. Use plot_data(p, "matrix") to extract the matrix from a saved plot p.

Interpretation

Positive "obs_exp" values mean observed scores exceed model expectations; negative values mean they fall below expectations. These values are in score units, not logits. The "t" metric is a scaled residual without a calibrated test or p-value. Color and optional threshold outlines are descriptive; an unavailable cell is not a zero residual.

Heatmap appearance

  • show_values = TRUE labels cells; value_digits = 2 controls rounding.

  • flag_threshold = NULL adds no flags. A non-negative value outlines cells at or above that absolute value; flag_color = "black" sets the border.

  • scale_limit = NULL uses the observed range. A positive value fixes symmetric color limits for comparing plots. It does not change saved values.

See also

dif_interaction_table(), plot.mfrm_dif(), mfrmr_plot_migration

Examples

ratings <- load_mfrmr_data("example_bias")

fit <- fit_mfrm(ratings, "Person", c("Rater", "Criterion"), "Score",
                 method = "JML", model = "RSM", maxit = 300)
diag <- diagnose_mfrm(fit, residual_pca = "none")
int <- dif_interaction_table(fit, diag, facet = "Rater",
                             group = "Group", data = ratings, min_obs = 2)
heat <- plot(int, type = "heatmap", metric = "obs_exp", draw = FALSE)
dim(heat$data$matrix)
#> [1] 4 2
# Obs-Exp is in score units, not logits. A scaled residual
# (metric = "t") is descriptive, not a calibrated t-test.